What was the caliber you submitted on your form1? I hope you did not put multi. I thought that was grounds for rejection, but this may have changed.
I have a 10.3" SBR, 5.56, and I think its a blast to shoot. I need to swap in an H or H2 buffer to slow it down some. I am using a 51T Brakeout, and it does throw alot of muzzle flash, which is something I am going to have to correct before acquiring NV.
Did you put down 10.3? or 10.5? for your barrel length? 10.3 would have opened up a couple more possibilities for you in the realm of barrel selection, but Im not sure if the ATF would throw you to the wolves for that. Havent been down that road.
I'd figure out the purpose of the weapon first of all, then go from there. Obviously the rifle wont be used for long range applications, but will be effective to 300 yards without question. Is it a carbine class gun? Just a range toy? Home defense? Safe queen?
Answer this question and then go from there IMO.
I personally and trying to go clone route with a CQBR blockII clone. It needs a lot of parts to get clone approved, but right now the platform is doing well for me. Just shoulder the rifle the way it is supposed to be shouldered and recoil shouldnt be an issue at all. That being said, I've never fired a .300 BO before, so I wouldnt have the subjective knowledge to compare the two in terms of felt recoil. Do you have other AR's? What calibers are they???
I would say keep them standardized unless you're bored, can afford all the ammo, or just primarily a collector and not an avid shooter. Nothing wrong with any of those, but may influence the build process.
In terms of saving the scratch, Primary arms usually has sales of 15% off triggers every few months. Since this is one of the easier mods to a rifle, just wait one of those out. As far as the other parts are concerned, Buy once, cry once. I've learned this the hard way. Its difficult to be patient to wait on that right part to come along, but they're out there. keep an eye on the EE here once you get your parts selection solid. Might find something come over that you cant pass up.
Oh and BTW, I got my form 1 back in 66 days. Mailed in late may, had the stamp back in July. My wife's was mailed same day, it came back a month after mine. Hope yours comes back that quick. Good luck with the build!