I have a suggestion:
Necromancer Falmer.
Specialization: When Falmer attacks a unit on the map, the necromancer infects it with a plague. Part of the unit dies. The percentage of units that die depends on the hero's level and the unit's level.

If you're interested, I can help with the implementation.;)

Like in Disciples? ;)
Psathi had a similar idea. You can create it yourself if you want, on any test map, and I'll just transfer it to the mod ;)
At least it will reduce the workload on me (although Ment is already doing a great job). Otherwise, there are still a lot of them to create... :p

Added 54 seconds ago

when will the mod be available?

Probably by the new year.... We're still collecting suggestions and people to implement them.

Added 13 hours 36 minutes ago
FIX
Sandro's army growth now depends on the number of units in the enemy unit, time, and the hero's level.
UP
Velund - a dwarf, specialization description: Can create artifacts. At least once a week. The strength of the artifact and the drop rate depend on the hero's level and the time since the previous forging.