I have thought about mods myself. I like the bass so much, though, that I won't do mods on this one. I could get another and use it for a guinea pig, though!
I wouldn't want a second humbucker, since I've had a Stingray Special with dual humbuckers and never used the neck humbucker at all (just didn't like the sound much). I ended up selling that bass and buying a single humbucker Stingray Special (which I love).
But what I wouldn't mind trying on a short scale Stingray is loading it with the traditional two-band Stingray electronics (like the Nordstrand copy of the original Stingray preamp). I'll bet that would sound killer--I'd guess very much like an original (long scale) Stingray with a little bit more low-mid oomph. Might be something to try in the future...