Well, for those of you who actually do read a bit of fantasy you will see that there's different takes on the "zombie / undead" burning thing.
In a Game of Thrones the undead are weak vs Fire and dies relatively fast when put to the torch. Vampires and some other entities does not exactly enjoy fire either and most vampires get's a penalization when exposed to sunlight ( some even burst into flames
)
As for the fact that a mummy can raise litterally hundreds of undead in an instant it is mostly problematic in adventure mode since they are not limited to tombs, but can litterally appear almost anywhere underground (temples, forts , tombs , sewers ) .
The bonuses for weapons is mostly an old thing coming from ad&d where it was more difficult to do damage with a piercing weapon on a skeleton than bashing it to smittering with a mace type weapon. Sure if you had a big enough sword you could probably hack the skeleton in 2 pieces, but again you had a damage penalization.
In DF skeletons and Zombies are way more lethal since every body part you separate can be "reanimated" and ensures a lot of fun for unlucky adventurers!
Basically being able to add something like Weakness:Fire , Weakness:Blunt , Weakness:Holy could be a big help when modding or making sure that a mummy can't reanimate several hundred undead at once but would reanimate corpses around them over time and would have a limit on the number they could control effectively. An effective range would also be desireable where either the undead would collapse or they would loose direct control over them.