I don't know if anyone else has been thinking about this or anything, but I think the old walls from BFME should come back, just not as pre-built. There is a mod that had done this with the base game of BFME II but that adds a few (in my opinion) ridiculous things including gunpowder based units and cannon defences. I think it would be super cool to see bigger walls come back and actually be able to man them with your units, while this might make it a little unbalanced towards the Evil factions, their battle towers could be a little stronger or be able to use palisades or something maybe. An increase of health slightly would also be cool, just because a thick wall isn't going to drop in just a couple of hits, maybe able to take 6 hits from a trebuchet or something, I don't know, it would just be super cool to see these return.
(I'm not certain if this is allowed to link the mod I am referring to, if not then I apologise)