this change isnt from a playing perspective but from an editing one, and im not sure if it would work or not, but:
would it be possible to make a few base UNITCLASS_HERO1 types, instead of a unit class for each hero? you'd prolly only need two for civ based heroes and 2 or 3 for religious ones, and 2 or so for non-aligned ones.
the reason i ask is that itd be a little easier when making them and editing those files, and would shorten the list for each civ under their unitclass declarations.
there are some concerns i have about it, like the base class being buildable themselves (though could make one civ and religion have the base classes), or that the game wouldnt allow you to build 2 of the same unitclass due to national/world limits despite being different derivatives, or that you might only be able to make them all available with the same techs, etc.... but if my concerns aren't real and its possible then itd be nice.