On looking at the schematics, I would say that the resistor is only used to reduce power using their hi/lo switch. I always wondered why these bulbs are rated at 82v...
Basically the diode and fuse should be enough...
http://www.kmr.com/manuals/dukane/3127/3127_05.htm
I started with the sunsplash 4123 (the lower diagram) which uses an FXL. I found the bulbs going cheap for about $6.50 on yahoo shopping:
http://shop.store.yahoo.com/cousinsvideo/fxlprojlam.html
I had the variac lying around, and used it to soften the hit to the bulb at turn-on: the bulb's resistance is lower when it is cold, and it draws a current spike for a fraction of a second until it heats up. In that fraction of a second, it gets much hotter than normal, and is most likely to blow at this time...
I didn't notice much of an improvement in lifespan, though, and at ~ $6 a pop, it probably isn't worth the effort.
Bill.