It is certainly possible but before you go to all the work that could be entailed it is probably a good idea to look at a couple of packages that have been released already. That is because they may already do what you want. First is the PRC and the second is the community patch. Also there are smaller packages available as can be seen in this small selection (which is what you get if you do a search for the tag "PRC").
To a much lesser extent you may be able to do some of what you want in the toolset, otherwise it will be a matter scripting. In the latter case you would be advised to ask questions relating to any problems that brings up, in the scripting forums.
Don't get me wrong, I am most definitely not trying to put you off, it is just that in computer terms NwN is very old (10+ years) and over that time some very talented (and groups of) people have solved a lot of omissions and problems. In fact some of them now actually work in the games industry (yes six I mean you).
Bottom line - if you want to try your hand at something in NwN - go for it and don't be afraid to ask when (everybody gets stuck sometime) you have a problem.
TR
