Good points. It seems that al-Muktafi should also be considered quite capable, and really ends up finishing some of the campaigns started by al-Mu'tadid. Even if al-Mu'tadid did live longer, I suppose he can only campaign for so long.
While the Abbasid faced threats and structural problems since the 9th century, is it correct to say that the ascension of al-Muqtadir and his unstable reign is what begins that final stage of terminal decline for the Abbasids? If so, would replacing al-Muqtadir with a different and more effective successor buy some time for Abbasid Iraq?
Possibly, yes.
The Abbasid state is not in dire straits quite yet at the death of al-Muktafi and it can be said that al-Muqatadir was a massive boon for the peripheral enemies, especially the Fatimids and other nearby foes. However, some of the issues that occurred within his reign were not necessarily caused explicitly by his policy. The reality of Turkic dominance that once more took control over the court, was not a mechanism of al-Muqtadir, but of his predecessors a century ago, who relegated much of the military functions to Mamluks or Ghulams. The Anarchy of Samarra some 40 years prior to al-Muqtadir carried similar issues and we see overt Turkic dominance in the Abbasid realm as early as the execution of al-Afshin in the 830s. In fact, the falling of favor of various Iranian generals and governors gave the Turkic specialists far more power than previous. Especially when one considers the level to which Iranian or Arab-Iranian leaders either were purged, rebelled or killed one another. Another issue al-Muqtadir could not control, was the receding economic prowess previously in place. During the years of the Anarchy of Samarra, one could say despite the upheaval politically, that the economic situation was not of a poor quality. In fact, the slave markets which provided a fair amount of wealth incoming Iraq, seemed to be in health.
As well, the farming, of all kinds, remained lucrative in the famed Sawad prior to the Zanj revolt and the effects of a decline in the Sawad only became realized later, with declining outputs from the Sawad region, that could more or less be owed to the expected population decline and the avoidance of the previous slave driven farming systems that prevailed throughout the Abbasid period prior to the 870s. It should be understood that the Sawad region and nearby areas were devastated by at least three consecutive wars that may not have individually crushed the areas, but cumulatively had effects. During the Zanj revolt, outside the obvious decline in productive slave owners and mass confiscation of land by Zanj officials (do note, the Zanj commanded a state apparatus and ruling centre, it was an extremely sophisticated rebellion), the local trading practices were disturbed. During the Zanj rule of the region of the Sawad, merchants previously associated with Baghdad were forced out and without permits, merchants had their goods confiscated and often the merchants were taken as prisoners. The Zanj operated more within an extended trade system with the Arab Bedouins to the south and the trade from the south flowed toward the capital of al-Mukhtara and those merchants who operated in conjunction with Abbasid fiscal growth were either positioning themselves in relation with the Zanj or forced out of business. Zanj economic centres and modes were obviously disrupted subsequently after the fall of al-Mukhtara. Following this, we have then Arab tribal agitation, usually in the region of Kufa-Najaf-Karbala, all of which carrying the sort of Neo-Shurha ideology or Shi'i mentalities. Then consequently, within Kufa, Palmyra, Sawad, al-Ahsa, Bahrayn, etc... the Qarmatians rise to pwoer and once more devastate these regions, in ways similar to the Zanj, especially in Syria, where the destruction was perhaps more total with regards to trade disruption in al-Raqqa, Palmyra and Damascus. These issues and woes were far outside the control of al-Muqtadir.
So, after addressing a few of my concerns in simply blaming al-Muqtadir, it should be known his own frailties. As a ruler, he is often painted as a sort of feeble man controlled by his mother and other court officials whose positions we can assume, revolved around internal Baghdad politics. This character is opposite to the constantly on-campaign al-Mu'Tadir, his father. Typically, this assumption of having a ruler tied to a single city and focused on various political and obtuse issues such as would occur in major metropolitan Baghdad with its divergent ideals, intrigue and the ability to create disconnect, is seen as a major reason for the fall of the Abbasid realm. Generally, this may be partly the case, many of the rulers to whom the consideration of poorly ruling is conferred, are those whose reign were of some sort of Baghdad or capital/urban centered politck. Further, many of these leaders fell into a deep seated decadence within the city life that separated them from their populace. However, on the other hand, it should be mentioned that al-Muktafi was one such ruler. His rule was exceedingly cautious and deeply Iraqi in its outlook, and thus his reign was fair and tolerable.
The primary difference thus between al-Muqtadir and his near predecessor, al-Muktafi is what? In my estimation, it can be accounted partly or wholly to the men in question. Al-Muktafi whilst a sedentary leader and delegating much to his Turkic mamluks and officials, stood his ground in political matters within Baghdad and held to a general ethos and policy that was not controlled entirely by varied Baghdad political cliques. Al-Muqtadir was the parallel, his policies were at the dictates of Baghdad political intrigue and obviously influenced by his strong willed mother, who despite any positive qualities, was likely unable to comprehend the issues on the exterior regions of the Abbasid realm and the dangers close at home.
My contention would thus be, to somewhat change or rectify the policy of al-Muqtadir toward a tempered version of the earlier policies and similar spending schemes as his two predecessors. That being, continued prevalence of military budget to keep his constituent military allies satisfied and the decreased spending on frivolous expenses such as enlarging the number of concubines or useless building projects. This is where the issue becomes near asb though, it is difficult to imagine a al-Muqtadir who is not swayed by his mother and her allies to focus on Baghdad and the internal court. The disconnect is there, Baghdad inspired a class of people in the Abbasid realm that ultimately lost sight of the empire and gave to themselves a false view of their own might as to see continued military budgets as not needed. This drop in spending was the result of the complacency of those intellectuals in Baghdad and court officials tied to Baghdad to such a degree that the view of stability became something that was taken for granted. Al-Mu'Tadid knew these perceptions were false as he rose to prominence and forged by the fires of wars occurring near Baghdad, the Zanj rebellion and the Safafrd-Abbasid war. Despite my opinion however, one can change individuals with the change of fate, see Octavian as an example of a naive individual to whom control by his mother was plausible in his early career.
As far as the policy, with knowledge that the views of al-Mu'Tadid and al-Muktafi were effective and preferable; the preference that I have regarding this would be that the Abbasid realm become tied to difficult conflicts to the west, against surging powers. Instead, the view I hold, would be that the policy of al-Muktafi's tempered regime continues indefinitely in policy. The Abbasid realm is perhaps to devastated by the previous century to reconquer Egypt, Syria, Arabia, Iran, etc... and expect to hold all these areas. It is similar to how after decades of inaction and decay, the Byzantine collapse after Manzikert stifled the ability for Byzantium to even try to conceive of itself as some hegemonic force. The Abbasid realm was in this position more or less, broken by various wars in its primary lands and nearby enemies present themselves with a vigor the Abbasids no longer possess.
Abbasid policy should focus upon Iraq and nearby areas and prioritize in a realistic sense the areas it should conquer and attempt to hold. Egypt is the worst option, it has been a hotbed for revolt and war since the Tulunids and subsequent failing Sunni realms there lead to the rise of the Fatimid regime. In addition, areas such as Arabia become more and more difficult to hold. Oddly enough, the Hijaz region could be more easily controlled if the connection to it was not blocked by what can jokingly called the production centre for rebellions of both Shi'i and Shurha/Khawarij variety. The region further is inhabited by powerful and independent tribes who dislike the Abbasid rulers. The north toward the Byzantine Empire is certainly not the region with which the Abbasid should be engaging, in fact, the Abbasid poltical climate should be one of allowing its enemies, namely the Fatimids fight the Byzantines, while making preparations for eventual conflict. With regards to Syria, the main issue is securing the cities of Palmyra and Raqqa. Each are the networks which allow trade to reach the Abbasid heartland. The other sections of the Levant could be viewed as difficult to hold, with knowledge of the enemies in Egypt and Byzantium. Iran in my opinion, should be the main interest in Abbasid expansion. That being, removing the need for the western realms in terms of trade for a time, by securing its routes to the east and remaining a powerful entity in the region and restoring its jurisdiction to benefit from the age of intensified Muslim incursions into Hindustan bringing the Abbasid legitimacy of destroying the infidels as well as gaining booty, especially precious metals and slaves.