yes and no. No. No.
I will draw on a whole lot of what works from HoMM, but not all. I want to allow for better integration of units between factions. Already in game, there are several means of achieving that. Such as infinite creature slots and adventure buildings giving cross-faction units. I do not want to punish a player for finding and using units of a different faction.
Moralewise, each point of morale gives a chance for units to enter "super morale mode" for five seconds where they move and attack twice as fast. It isn't communicated particularly clearly right now, but that's a work in progress thing. Currently negative morale does nothing. It probably should do something. But not the flat "lower stats" model you suggested.
Undead and 0 morale - well, that's a conundrum. Let's do a pro and cons list:
Pros
- "realistic"
- asymmetry between factions
Cons
- losing a strategic aspect
- esoteric
- a good artifact might suddenly become useless because of your faction
To me, it feels rather pointless, but if you have a good argument for why I should do it, I'd be interested to hear.
And maybe maybe mixing specifically undead and humans/elves should give a negative effect just for the sake of immersion, but it would have to be more interesting than a flat bonus. Like your units attacking eachother or something like that.