About to do the same myself with the K100.
The forks are 42mm, so no hassle getting brackets and a headlight. The indicator circuity is typical over complicated/low quality BMW, so no hassle if you'll just bin the tupperware and plug in a standard indicator, but could be a PITA if you want brighter bulbs or LED's.
Take care with the throttle cable routing. To add a few grammes of ballast the K bikes have this stupid cast monkey metal bevel gear in the throttle housing and weak springs in the fuel unit. Route the cable wrong and a stiff throttle is closely followed by stripped gears in the bars. As I know to my cost that's 40-quids worth of monkey metal.
I havn't got this far yet, but I think I'm going to have a water trap on top of the radiator. I'll decide when I get there between trying to source K100 bits and getting the hammerite/fibreglass out. Good news is that the air intake on the 1100 is round so will take an external filter. Cut the middle out of the one in the sandwich box under the tank and you'll be able to replace the air filter without taking the engine out. I'll be sourcing a round K1100 intake to replace my square K100 one.
If you wouldn't mind getting your lardy bits on e-bay PDQ it'll make mine go for more in a few weeks
. Seriously though, do it, I ripped out the cassette player (complete with Frankie goes to Hollywood C90 (I was expecting at least Kraftwerk)) and got 30-quid.
You do know you'll get blackballed by the BM club though. My suggestion of stripping the K100 did not go down well. I even offered to paint the fairing white and add a lime green stripe before I flogged it off
. Please keep posting how it goes though it'll be good to compare notes.