There’s been a lot more refinement in the past 50 years than furniture.
1) The tweeking to get everything from 20” Rifles to 10.3 Mk18s to run reliable including when suppressed.
2) flat tops for optics have been the biggest game changer. Few other platforms are as optics friendly. From RDS, to ACOG, and $30,000 thermals.
3) rail systems allowing mourning of IR lasers and lights are more than just “furniture” IR lasers and NVG are a real advantage.
4) the adjustable LOP on the CAR / M4 style stock.
I don't know anything about the current production M1 carbines other than not hearing great things. I have an original Inland carbine that runs enough to be fun and it's light and handy as can be. If someone did manage to make a repro that met our current expectations or reliability I would be super interested. Something like a Fulton M3 Scout carbine with type 2 barrel band to take to visit friends in California.
I doubt Brownell's will tackle something like that any time soon. I'd rather they focused on AR clones for the time being anyway. I want to see them start doing A2 fixed carry handle stuff.
In the P-F basket of deplorables.