All things considered including collectable, historic and so on I don't see any real benefit in doing that. There are plenty of other options that out weigh a modified Garand.
If you have enough spare parts on hand to build what you want it would make for a cool project but I would build the real thing.
What I would like to see is a company that will produce a real M1A / Garand in 6.8 and 16"-18" barrel and I'm not talking about a Mini 14.
I wish to be remembered that I was the last man of my tribe to surrender my rifle.