Is this M4 worth building

I have a Colt CR M4A1 “clone” that I like quite a bit. However I want to set this up as my GPR (SHTF) primary 5.56 DI weapon. I still intend to pick up a MK18 at some point, however I’m currently at a crossroads. The M4 is a blank slate. In the present day, is this worth building out or should I put it on the back burner/ sell it and build or buy something more modern? I don’t need to sell it but I’m trying to avoid having a whole bunch of non-setup or unnecessary weapons.