u can add needed mods (on description page of ur mod click right on "add needed items").
i try to give mounts to spy and branchwraith (and mixus shadowdancer). but its hard to finish, i think i need new models for spies riding sth. u could help a bit with ur knowledge, if u want.

I have updated the mod so now Drycha gets Melkoth's Mystifying Miasma instead of Pendulum.

That is a good point, I will add it to my list of things to change

You might want to reconsider Drycha's spells, her special skill, Indoctrinator, reduces the winds of magic cost of Melkoth's Mystifying Miasma, which is pointless if she no longer has that spell, or unless you change the skill to affect some other spell.