It is pretty much possible for a luthier to do anything you could ask for to a guitar. Bigsby's are pretty common on les pauls / SGs etc, and I've seen them on tele's as well, so that'll be easy - so easy you coud probably do it yourself. Can you really dive-bomb a bigsby though? dunno, I've never used one...

The kahler mod would be easy enough for a pro, and as you say kahler make bass trems so it'll cope but as it still uses springs to offset the tension, I can't see it being much better than a floyd (I have no experience of kahler trems - just applying some thought to it)

I love floyds - you just need to get used to them. I've got graphite saddles which maybe help tone - although I've never had a problem with tone on floyd equipped guitars. On the pain in the ass string changing, without wanting to sound patronising, it's an experience thing. It's also made easier by using a wedge of some type to hold the bridge up while you remove the strings - saves you the constant messing about bringing all the strings to pitch. I've used floyd rose bridges for years, and could at a guess totally restring and tune up one of my JEMs in a few minutes - definitely less than five....

If you only need the dive-bomb, have you thought about using a hardtail and a whammy pedal? You'd get the tone you want, plus tuning stability and no worries with string gauges (beyond making sure they fit the nut/saddles). Removing the amount of wood required to mount a kahler is bound to have an effect on tone...

Oh, and if you see a pink 80's 'hair metal' guitar, buy it man. Everyone should have a pink guitar :D