There was an attempt to reform the Empire from 1434 to 1438 as a reaction to the Hussiten wars which convinced the nobles that a more active central power could be useful. However this didn't went anywhere because the emperor wanted to increase its own power while the nobles wanted a central power in which they also had an influence and neither party was interested in compromising, once the hussites were defeated.
However in 1437 several minor nobels, parts of the church and free cities proposed a compromise, as they feared the power of the Dukes and hoped that a stronger central power would protect them. This compromise - which would more than a century later be considered again under Maximilian I - included things like an independant court (Reichskammergericht), a unified military (although the nobles would be allowed to keep their own forces) unified currency, and an assembly of nobles which should govern together with the emperor. As the Hussiten were defeated no one was interested in this proposal anymore.
But lets assume the Hussiten mangage to hold out for longer, which is not to improbable as the battle of Lipany was only lost due to a deception, the proposal might be accepted.
If its impelmention is succesful (which is far from certain, but as France was still involved in the hundred years war there would be less outside interference) this could lead to an unification. Although some civil wars are likely to be fought over it.
I agree.
-The unification of Germany itself is going to take several decades.
Yep.
-Italy and Switzerland while still nominally part of the Empire were de facto independant for centuries. As soon as a strong central power is established in Germany itself (wheter it is centred around the emperor or the nobles) it will try to reassert itself in those areas. Of course this will cause resistance by the swiss and italians and lead to several wars. While Switzerland may be reconquered, there is no chance that northern Italy will be regained. Of course the Germans won't admit that before they are defeated several times and even then they might develope an obsession over Italy like France did IOTL.
The development of national self-consciousness were still quite partial and reversible in 15th-16th century Switzlerland, and as it concerns Italy, our educated elites were particularistic (but no more than the German ones themselves) but still quite captivated by the imperial ideal, too. The 1400s-1500s were centuries before Italian nationalism would be born. Italian nobles and city-states had asserted effective independence from the Empire for pretty much the same particularistic reasons and in the same way that German nobles and city-states had been. Northern Italy was an integral part of the HRE just like Bohemia or Austria. If a centralization of HRE is successfully pulled, northern Italy is in all likelihood going to be a part of it.
True, France is going to object, but some wars with France are going to happen anyway, since there were other parts of the HRE-space (Low Countries, Burgundy) that the reborn Empire is going to reclaim and France deems part of its turf, too. If the process is successful, and those wars are won, northern Italy is going to be reclaimed, too. An interesting issue is what happens with the Papacy and southern Italy. France needs to be defeated in war anyway, but Spain had ambitions on and dynastic-economic ties with Southern Italy. A compromise may emerge by which the HRE keeps northern Italy and Spain keeps southern Italy. Or the Empire may win a war with Spain too and keep Naples (maybe Spain keeps Sicily and Sardinia, or maybe not).
An interesting issue is what is going to happen when the Protestant Reform hits (or something much like it: the Catholic Church was so corrupt, greedy, and theocratic that something major in Europe was going to happen to put its political power and economic privilege into question, maybe with different faces: ask the Lollards and the Hussites). If the HRE Emperor pulls a Henry VIII and takes the lead of the Reform in the Empire, creating an "Imperial" Church much like the Anglican church, in alliance with the moderate Reformers like *Luther, he may expel the Papacy from Italy and reclaim the Papal States, too, if not southern Italy.
-Speaking of france, half of the Duchy of Burgundy consisted out of french lands, while the other half belonged to Germany. IOTL France mangaged to aquire the lands relatively easy, as the disunited Germany couldn't put up much resistance, but with an united Germany this will lead to several wars.
Quite true. Some successful wars with France (perhaps in an alliance with Britain and/or Spain) are necessary in order to successfully reassert the united HRE in its integrity. There were too many valuable areas with conflicting claims: Burgundy, Low Countries, Italy.
- The german order and poland had several wars, and some german nobles supported the german order, which led to poland supporting the hussits.
Of course, with a strong united HRE, Poland would be much less successful against the Teutonic Order. Esp. if the HRE goes Protestant, it may easily absorb the TO. Poland would likely fail to conquer West Prussia and would remain bound in the mid-1400s borders vs. the HRE-TO combo. Of course, with a HRE unification in the 1400s, Poland had already gotten quite sturdy and the moment to make the German eastern expansion any more successful than it was IOTL had long gone.
- The Ottomans were subjugating the balkans and comming closer to German lands.
True. Not to mention that if the HRE unification is sponsored by the Habsburg emperors, they shall be quite interested in pursuing the personal union between HRE and Hungary and trying to deepen it to a real union. This shall bring the Empire to the forefront of fighting Ottoman expansion in the Balkans.
All this will keep Germany concentrated on continental affairs for quite some time. Of course this unified Germany will also posses the ports of the Netherlands and Flandern, so once it becomes obvious that the oversea possesion are valuable they are likely to join.
Well, we must not forget that IOTL Spain colonized quite a vast chunk of the Americas while being quite busy in European wars vs. France, Turks, Protestants. I see no good reason why the hRE could not replicate the feat. With a powerful united HRE already around, it is quite possible that the at least some of the explorers end up sailing for the Empire. E.g. with Genoa, Venice, and Tuscany in the HRE, it is quite likely that Colombo and Vespucci end up exploring the Americas under the Imperial Eagle.