JG M4 is fine. I hated the look to begin with, but actually it isn't bad. especially when painted. example
The mechbox is JG's old gen1, so it will need metal bushings, and a reshim and re-lube. It's fine for a beginner's gun, and if you don't like it, you can sell the plastic bits as a "M4 kit" and buy a new front end. Done.