I am looking to build my first light from the ground up. I have a few parameters I would like to stick to if possible. (They are flexible though).
A single 4000K to 5000K emitter running a single 18650 cell.
I would like as tight a thrower as possible with 1,000 + lumens.
Any decent host is fine, just looking for a project to do and all the parts I would need to complete the project. Yes, I know it is cheaper to just buy one, but I feel like starting modding. 
This was a nice blf thrower, perfect for a first mod experiment. Lots of info and different attempts in this thread. Curious how this would do with a flat white.
the venerable Convoy S2+ is a good choice. Just add 17mm driver, and 16mm MPCB with your choice of LED. I might suggest the XPL-hi, it throws nicely and plays well with the MtnElectronics Product Code: FET17-NUV
Toss on a flat top or button top 18650 and you’re up and running in 15 minutes.
Then you can add the LED light-up tailcap
Hard to get an old C8 nowadays (Type I, separate brass pill), but newer (Type II, integrated shelf) are still pretty easy to work on.
The S2+ is really easy to work on, but will get hot in a hurry if pushing out 1k lemons. Not a bad thing in case you want it to double as a curling iron, but…