I've seen a lot of MP Mods but are there any single player expansions/alterations? Recommendations? Personally I was hoping for enhanced combat/force powers.

Bit late with responding but have you checked the JKhub?
There are a couple of smaller SP maps/campaigns that I know of and there is a total conversion called the Dark Pastime in production but that seems to be the extend of it.

Sadly the series never attracted a lot of modders to do big expansions, probably because of the effort it takes.