If it is druids that interest you you might be enjoy Divine Remix over at
http://www.gibberlings3.net - we're adding kits from various source material to all divine classes, and doing a few other things.
One issue we encountered is that a lot of the pnp abilities do not translate well into the game.
You can't add an extra slot at creation for Avengers - you could, however, increase the number of slots they can place in a weapon, or give them a bonus proficiency with a set weapon.
You could do the Guardian's combat bonus with a script recasting the spell when in the appropriate areas.
The +1 CHR wouldn't really work; it also probably wouldn't make a jot of difference in the game since CHR is checked so rarely.
You could always write extra options into existing dialogues that take effect only if the charactye is a Guardian, but that might just suck up a load of your time.
Also, I'd suggest using WeiDU as the installer for your mod - NI is fine for making the spells etc. that the kits will use, but the best way to add kits is with WeiDU. See
http://www.WeiDU.org and CamDawg's kit tutorials at the G3 forums I linked to previously.