Hey Narc,
What you propose can be accomplished, but unfortunately the process isn't as simple as just swapping out hands. In the vast majority of instances where non-Traser brand watches are concerned, there's insufficient room between the face of the watch and the underside (inside) of the crystal to accommodate the fatter than normal tritium vial illuminated hands.
The most common solution to this problem that I've seen employed is to have a customized acrylic dome crystal made for the watch. The bubble-like shape of these crystals can then obviously accommodate the fatter hands with their glass tubes. I'd recommend visiting the Military Watch Resource forum. You'll find several individuals there who are knowledgeable in the art of "Frankenwatching" as they like to call it. A gent by the name of Hyunsuk Seung is probably the most experienced among them in these types of conversions, and sending him an email detailing what you propose would probably be time well spent. The MWR site even features a gallery of some of the work he's had done, and it's a definite must see.
I don't know of any large companies per se that are into doing these types of modifications, but there are some very skilled private watchmakers who can do just about anything you'd want. I've considered having something similar done in the past, but have thus far resisted the temptation primarily because the mods we're discussing here are usually not inexpensive, and, beyond that, I personally just don't care a lick for the easily scratched acrylic crystals that must normally be used (although most of the mil-watch fans love them).
