What, have I suddenly become
infamous famous 'round these parts all of a sudden?
Seriously though, any decently built Affinity would be a great platform to tinker with. And yeah, having a less-expensive beater/travel bass that doubles as a sort of "insurance policy" against overwhelming damage or loss is a good idea, especially if some of the places you gig warrant it.
What kind of mods did you have in mind, thumper? Pickups? New circuitry? Something cosmetic to spruce it up a bit?
If it were my bass, and I thought it needed a serious sonic overhaul, the first thing I look to are strings, but it sounds like you have that covered. Pickups vary with personal taste, but I'm taking a shine to the not-so-new Fender Super 55 split-coil Jazz pups. (I recently used one on a P/J parts bass) They currently go for about $45-$50 each on eBay.
Choose your P-pup carefully. I used a Seymour Duncan Quarter Pounder for my project. Ultimately, I changed it to a more mellow MIJ split-coil as the SD-QP was just too "clangy", despite my love of an aggressive sound. (maybe because the pup was placed a little closer to the neck than usual?)
For the wiring, I found a great harness made by Santellan Sounds at elek-trix.com.
It's a two-pickup, solder-less harness that can switch between series and parallel with a push/pull pot. They're currently sold out, but they say they'll have more before the end of the month. They go for $80, brand-new.
On a side note, I plan on contacting them to see if a three-way pickup selector can be installed before the harness to further expand the versatility and sound.
So, if I did the same mods to your Affinity that I did on my project bass, that would come to…
- Bridge (Jazz) pickup: $50
- Neck (Precision) pickup: $25
- Wiring harness: $80 ($75+shipping)
…about $160. You could go for different, snazzier pickups or maybe even a pre-amp as well.