Of the items mentioned so far I have heartily embraced the relatively recent D-class amps for their light weight and easy transportation. I sure wish those were around when I was younger, but they are especially a Godsend now that I am older!
I also got into graphite as a viable material for bass and have a few Status Graphite basses. The necks are very stable and stay true, but dead spots are not totally eradicated. I like the headless concept too, which makes the bass lighter and more compact. I would like to get the all-graphite Stealth model from SG, but its not available left handed. Grrrrr!!
Side dot LEDs have been helpful from time to time.
I have always wanted a Pedulla Buzz Bass for the shiny epoxied fretless fingerboard (a Jaco inspired innovation), but they are so expensive and I'd probably be so protective of it I'd never play it. So I had my fretless MIJ/Warmoth Jazz epoxied for relatively cheap and it has been a great poor man's Buzz Bass. I'd still like to get a Pedulla someday.
D-tuner is a great gadget on many levels. Easy to install with no mods, very robust, simple and fast operation, stays in tune. Standard equipment on all my headed 4 strings. I just wish they had a D-tuner device for headless basses. Wasn't there one that was like a knurled knob right past the nut?? It looked simple and fast, but it vanished from the market.
Although they were not available lefty (to my knowledge), I was very intrigued by the Guild/Ashbory bass and always wanted to try one. They were discontinued long ago, but the small size and silicone strings were so oddball at the time. I don't even think I have every heard one on a vid or soundbite. But if it had a viable sound and playability factor that would be the ultimate portable rig with some class D amps.
I recently tripped out on a vid of Muse bassist Chris Wolstenhome playing a double neck Status Graphite tablet bass. Not sure how it all works or how gimmicky it is, but it looked very interesting.
http://www.musewiki.org/File:Statuskitara.png