I used to buy lights just for the carcass, the Holy Trinity (SK98, WF501B, WF502B), then added C8s to my repertoire. Nice bespoke lights in whatever combo I wanted. OP or SMO, 4C or 5D or 7D, XM-L or XP-G or XP-E, N modes, M×7135, whatever you want.
Most of those were quite decent to begin with, excellent in fact, except for the cheap driver and at worst a LatticeBright clone instead of a real Cree. Then there was a race to the bottom to see who could outcrap the others, with plastic reflectors, lightweight Al pills vs brass, and it didn’t pay anymore to try to make silk purses out of sows’ ears. You’d be lucky to get a LB clone.
The only lights that start out with excellent quality that are easy to mod are the Convoys, and those purpose-built for modding (eg, Solarforce hosts). Everything else seems to be glued, soldered, welded, etc., and just not worth the ag trying to crack ’em open like an armor-plated coconut.
Now, most of the lights I get, I leave bone stock unless there’s something wrong with ’em. L2? Stock. F1? Stock. Q8? Stock. Stock, stock, stock. They’re good enough as-is for me to not be biting my fingers trying to mod ’em. Heresy, I know, but…