I think the Hold Out blasters would be a good choice. There are only 4 basic models, they are small (therefore easy to redesign), and I can easily make a few more that have different "elite" properties. It is always good to have a Knockdown Blaster and a Paralysis Blaster in one's inventory.
Incidentally, the sound the GoTo droids make when you knock them down is *hilarious*!
I think I'll also make all of the Ion pistols fully-upgradeable.
I don't know if I can make mines without getting into the .2da files, which I try to avoid. It is a very good idea, and you may want to post it in the Modding Request forum. Someone with TSL-Patcher experience might be willing to take it on. I certainly wouldn't mind seeing some new mines in the game!
~a short time later~
A HoB design concept:
http://i714.photobucket.com/albums/ww150/ajkfjaioIIl9Wkk/HoB001.jpg)