*Trawling for advice; trolling is what people do if they think you're asking for stupid advice :P
I've done a few mods and a few parts builds, and in my experience bodies will almost always require modification. Initially, I was very put off by this, but learning how to deal with it, it's a small obstacle. I've only come at it from the side of the neck being a little big, and that being the case I've found a Dremel Trio to be the perfect tool to work with.
Also, modding cheap basses into something good always seemed like a better idea than it was. Maybe it's exactly what you want, but I've always been disappointed with my results. Lastly, I've used a Badass bridge before, and it's nice, but unless you really hate the stock bridge (like I did on my Brubaker Brute), you probably won't notice much of a difference. Pickups, completely different story, go for your life.
I am Jack's neglected P-Bass|This is your gig, and it's ending one minute at a time|Yeah. Well. Whatever. You can't teach a guitard anything.