Heroes 5.3

To be honest, lol, how can you do without it? MMH5.5 was made based on the source code of version 3.0 (which remained in the shadows), and you want to adapt the mechanics of the fifth game to the mechanics of the third without it?
P.S. Here, only 1 in a million people knows how to fully export a complete model into the game without attaching pieces to it, such as effects, and you want to do something like that?

You should consider several facts.
1) It is not planned to make the fifth game exactly like the third. We are only talking about making specific changes to the most important things. This includes 2 classes per faction, more heroes, reworking and unifying the skill/ability wheel (only for the Necropolis, it will differ due to the presence of necromancy and the absence of leadership), and allowing Barbarians to use regular magic if they wish.
2) All changes are either related to reducing functionality - faction skills, "extra" abilities, faction buildings - or to changing parameters in XML. A specific example of such a change is rearranging the links between heroes and classes. Even the mod for new heroes, 240H, which is planned to be used in a modified form, was created without a single line of code.