The most critical front of all: the home front.
We certainly agree on the mean of any kind of Anti-Italian strategy. That's why my proposals always include the political need to entice Italy to the negotiating table and to reach an armistice as soon as possible.
Launching a huge series of offensives which will feed the casualty lists much faster and inflict more stress on Austria-Hungary than standing in the defensive while Cardona et. al. needlessly and incompetently sent Italian troops forward to be butchered against the Central Powers alpine defenses would.
But I would argue that if Austria-Hungary can harness the much more powerful German military machine for a "Caporeto II", there results are much more promising than standing on the defensive alone (or attacking alone as in OTL).
The Italian army and leadership in 1918 had undergone massive changes which cancelled out some of the folly and flaws of the previous years. Even on the defensive, AH alone would have a hard time dealing with them as soon as the Italians are geared for attack in the second half of the year. There would be hardly any stress-relief when compared to OTL. A retreat into the Alps might be a different thing and avoid a Vittorio Veneto. On the other hand, this frontline would again be much longer than the one achieved on the Piave.
Additionally, whereas the Germans were lacking, the Italian got some reinforcements from their Entente partners, turning the balance without more CP-emphasis on the theatre against Austria-Hungary.
By the way, I did a quick Wikipedia-check

eek

on the number of casualties during the notorious Isonzo battles. Though Italians numbers were usually higher, the difference is
not as big as I had expected. The k.k.-Army "coming apart at the seams" on the defensive would still be under massive stress, suffering from low morale as being on the withdrawal and see its time running off.
The A-H is already coming apart at the seams in 1917. Standing on the defensive in the various fronts the A-H is engaged in will give Germany a better chance that a stable ally exists to her south.
I am simply afraid that this would not be enough. Italy has to be
out for Austria-Hungary to come out of the war halfway in one piece.
However, in the end it comes down to what I always preach when it comes to the CP in 1917/18: diplomacy and territorial flexibility! In Italy, the same counts as on the Western Front.
If anything is doable for the Central Powers, than the military side has to prove successful - and the diplomatic advances have to be loud and seductive. [It would be very interesting to know from someone with a good deal of knowledge of the situation in these place how plebiscites might have run in Trieste etc].
And if an emphasis on Italy (with a clear and limited aim, i.e. a Garda/Adige-front) prevents the Germans from launching the va-banque-game of the Great Offensives on the Western Front, the cards would be mixed differently there as well.
In the end, France is the decisive battlefield.