How about head assemblies to fit M and C series bodies. Head assembly in my mind is
1) Bezel
2) Lense
3) O-ring or seal
4) Reflector
5) Main head portion (ie reflector housing with bezel screws into)
I like the Surefire heads, but the only problem with them is no easy way for user to replace components. For example...the reflector...if you are experimenting with different bulbs from Welch Allyn in Fivemega's bi pin to Surefire MNxx lamp adapter then you are afraid of bulb explosions ruining your $150 Surefire KTx head with no hope of repair. But if you make a head assembly with a removeable reflector we could either 1) Clean or 2) replace just the reflector. The same goes for the lense...user serviceable.
Also at the same time we could go with plain bezels, mild crenelations, wild crenelations, titanium, brass....etc you get the point...we all like our lego!
You could just design head/bezel assembly and use existing reflectors/lenses/o-rings...
Let me know if you want more ideas, I have plenty as far as this head idea goes, just not the money to fund a big project, and I do not like prepay (anymore).