Ma'an...............are you for real?
You're about to drop $15 K+, or thereabouts including optics & that's serious change.
I've tried a lot of stuff & built a lot of stuff, including 3 Knight's rifles including an LPR & 2 16" SR-15's so, here's my 2 cents worth.
You can easily buy 3 top shelf guns to cover your needs like KAC or LMT or JP or Radian or SanTan or....................
Or build them.
At the end of the day if you build, I'd direct you to 3 guns for starters, including losing the SBR...........just not worth the hassle & a 14.7" P&W'ed to 16" is mobile enough for 99% of most people's need & has a ton of flexibility & versatility.
If building then
1. 14.7" P& W'ed to 16", Craddock Precision (Rock Creek) barrel, mid-gas, 13.7" SLR, Geiselle MK-14 or Midwest Lightweight rail, SLR AGB, SLR or SanTan receiver set.
2. 16" lightweight fluted Craddock Precision (Rock Creek) barrel, intermediate-gas, 13.7" SLR, Geiselle MK-14 or Midwest Lightweight rail, SLR AGB, SLR or SanTan receiver set.
3. 18" Craddock Precision Bartlein straight fluted barrel, rifle gas, 13.7" SLR, Geiselle MK-14 or Midwest Lightweight rail, SLR AGB, SLR or SanTan receiver set.
Some commonalities
Whatever you want for MD / suppressor, White Sound FOSSA, flash hider if not suppressed.........virtually 100% flash suppression.
JP, Young Mfg. or RCA bolt carriers across the board, HM Defense improved bolt with blind hole for cam pin...greatly improves strength of the bolt. (Young was selling them as a unit, not sure now; HM Defense also sells complete units)
If you don't want an AGB, look at RCA's adjustable gas key & bolt carrier................Equals the performance of most AGB's But you have to remove the BCG to adjust it.
Geiselle charging handles are top of the heap, as are Radian's Talon ambi or single sided safeties. Period.
Plenty of good barrels & suppliers, but Paul Craddock has been so good to work with that I find it really had to not buy from him, but CLE, & WOA are also great, WOA just not as flexible as the other two. Both Craddock & CLE offer several blank manufacturers to choose from. WOA is a bit more limited both on blank choice & contours.
Geiselle SSA-E Two-stage triggers across the board, no need for more, & you'll regret less.
Just my thoughts............you can do all that needs doing with the above.
As for optics, an Eotech on the 14.7". a NF of your choosing on the other 2. NF has great QA & they make an offering for however you might want to configure a rifle.
Options are endless, ever body to their own desires.
JMHO, YMMV
MM