Me too. I've got an original SP1, and a retro built around an original USAF upper and barrel, and the only A2 thing I've added to them is the square front sight instead of the original round one.
I would love to have an SP1 to go along with my AR-180. I may just build up a SP1/601-ish copy so I can have one...kinda brings back some old memories.
And I'm 100% in agreement. Just like the round handguards, the square sight post was just one of those "well-DUH!!" innovations that was LONG overdue. So my SP1 will get an A2 front sight post, and I'll probably put on on my AR-180.
That round post would throw you off just a touch if sunlight was coming over your shoulder at an angle. It would reflect slightly off the side of the post and unless you were just carefully shooting targets you wouldn't notice that your aim was slightly to the right or left depending on which side the sun was coming over your shoulder.
What I have in mind for my build...
For some reason I recall the M16 I qualified with in basic, and that ONE M16 has always kinda stuck in my head. There were a lot of mix-match M16's in the Army but this one stood out as being just a little more "Franken-16" than most.
It had a partial fence lower, which I clearly remember because that was the first time I had ever seen that, and I was a little perplexed. So I'm sure it said XM16E1 on the side, but I don't recall ever looking at the manufacturers marks. It had a fully chrome bolt & carrier, but the carrier did have the serrations for the forward assist. Both of those features are typical of an early XM16E1 or 603.
The buttstock was the late style with the trap door, and it was darker black than the pistol grip & forend (or anything else on the rifle).
The flash suppressor was still the old 3 prong, and it was the 3 prong flash suppressor that caught my eye when we were grabbing weapons. I knew it had to be a very old M16, was probably beat to shit and probably didn't shoot worth a crap, but I wanted to shoot an M16 with a 3 prong, and by the time I went in, 3 prong flash suppressors were very rare. Surprisingly it shot pretty well and I easily qualified as expert. Since it was a 3 prong flash suppressor I assume that rifle had it's original barrel...I have no clue if the barrel was chrome lined or not; probably was.
Those are the only details I really remember of that rifle, aside from it missing at least 50% of it's finish on every square millimeter of exposed metal. I can't explain why I clearly remember and can picture that one M16, but I can. So when I build one up, that's what I'm going for. I don't care if it's "correct" for any one model, it will be "correct" to me.