Hi man, after a quick read i have this questions/points:

Imo, this is as bad as a naked tranny hidden in your garbage bin. You might say that you cannot grant a specialist with an USR if that is already present in your army. SO, if i have a spece marine, i cannot give anyone ATSKNF and so on.
All in all, i'd say that you should give less restrictions. In such a small pointset and peculiar gaming enviroment, its easy to crush the game in an unplayable thing.
Cheers
What if i don't take any character in the list (say 5 nurgle spawns)?
Why this? you are still allowing beasts with no limitations. Imo there is no need to limit the amount of mounted/fast troops. They are powerful but costly as hell. Also, this way you are crippling Eldar and Dark Eldar (that notoriously struggle in this format) Also, about limitations, what about wraithblades? they are legal in this format and they will kill you no matter what (especially if i cant outmanouvre them due to no fast models)
I'd rather say, if limiting power creep is your intent, no more than 2 wounds. This way you remove many nasty critters that could ruin our little game
Limiting specialists that way is a non sense, imo. So, if i wanted to take a kill team of say, plague marines, (6 PL Marines, 2 plasma, powerfist, 199 pts) i would forfeit all the specialists?? Since all plague marines come with FNP built in...Also, dark eldar: all have fleet. no specialist for them. Also space marines: all have ATSNKF. No specialist for you.
Imo, this is as bad as a naked tranny hidden in your garbage bin. You might say that you cannot grant a specialist with an USR if that is already present in your army. SO, if i have a spece marine, i cannot give anyone ATSKNF and so on.
All in all, i'd say that you should give less restrictions. In such a small pointset and peculiar gaming enviroment, its easy to crush the game in an unplayable thing.
Cheers