Unfortunately, there were too many changes made in DKS (PC and Xbox versions) to maintain saved game compatibility with D2:ED (redesigned flying fortresses, changes to enemy placement and loot, etc).
On the PC, saves made in the original release of Ego Draconis are compatible with the add-on FoV (digital download only), but Larian could not get just the add-on published for the Xbox.
The battle tower servants are chosen randomly when you start a new character in FoV (I just tried it, and got Igor, Hermosa, Barbatos and Radcliff), so if you don't mind going through the beginning several times you should be able to at least get a couple of the servants you want (there is only a 6% chance of getting all 4 of your picks, though).
Welcome to the forum.
