[Kristoffer O]

1) No, unfortunately not.
2) Don't think so.
3) Differentiated stealth capabilities are not possible.
4) This is not possible. Area of effect always hits every one in a square, but there is a defence save on some spells with AoE (Falling frost and earth quake). Don't think it is available on weapons though. Several attacks will not solve your problem either as one weapon only attacks one target.
5) Not possible either IIRC.
6) Not sure. Someone els might have to answer this. Try Liga's page.

It is not possible to add a mod as a theme. It has been wished for, but according to JK it is not easily implemented. The themes are sort of ad hoc coded and to add and change themes by modding would demand a remake of several parts of the code.