I eagerly await the Lion in Winter section of the TL.
About the ToT, I think I've got some ideas about where the different theaters are going to be.
1. Demetrios will try to ride out the storm in Egypt due to lack of interest in being Emperor, but either one of Andreas' other sons will view him as a threat (he is firstborn son, after all) and pick a fight with him or whomever momentarily wins Constantinople will be such a monster that he feels honor-bound to go deal with the situation.
(Leo maybe?)
2. Andrew "Arpad" will make a claim of his own and push into Roman Italy or into Serbia. If he doesn't get involved until later, perhaps it's his son (who is a legit Apard AND a Komenenos). If the ToT has been devastating enough, the Byzantines might not care he's a foreigner and a Catholic.
(Although I imagine they might want him to convert.)
I suspect it might be a younger son, since a Hungarian-Byzantine dynastic union would be too big and unwieldy to last long.
I almost sure B444 has said it's going to be a son of Andrew to enter the fray, so I guess the most likely round for a hungarian intervention is the second.
I do think also the Milanese will be players , but I pick them to be active in the last round after the Hungarian pay dearly for their intervention.