Carte blanche shorty build

[mcantar18c]

I'm building a 11.5-12.5" pistol+brace (to be SBR'd at a later date). I can get pretty much any parts for it that I want, but the cheaper I make it the more cash I get on top of it.
I have a week or 2 to put together this parts list until my buddy gets the back pay from Uncle Sam to fund it, so a small backorder time on a part isn't an issue. I'm looking for suggestions on parts... which to choose and where to find... and I really just need a sounding board for my thoughts.
Prefer 12" even, but a half inch in either direction is acceptable. I know I want a KX3/KX5, a BCM medium charging handle, and obviously the Sig brace. I definitely want a free float keymod handguard, and I want it to be longer than the barrel but not more than 1", preferably less, but that means it has to have an inner diameter large enough to accommodate the KX3/most suppressors. I'd also like the rail to have keymod holes on all 7 sides like BCM's, not just 3, but that's not as important as proper length. I'd strongly prefer a hammer forged barrel, although I can't find any in stock other than an 11.5" on BCM. Blem/demo uppers and lowers are preferable but nobody seems to have any in stock. I really like that HSP light with the slanted back, and I'd like a hand stop that takes up as little space in front as possible (i.e. not Noveske's). I'm also going back and forth between a T1 micro and a dual-illuminated RMR, both have their qualities.