I'm gonna say "no", don't do it. I love the M15's, my nearly pristine dash-4 was made in 1980 and it's as sweet as they come. But, they ain't worth a whole lot of money, nor are they difficult to replace.
Looks to me like you have a nice beater gun, I'd love it for what it (currently) is, and be on the lookout for a nicer one, if that's what you want.
But, a new finish will diminish any future value and collectibility, and is going to cost around half of what another M15 would cost you. If money is tight, then it ain't a good idea, as it's a frivolous waste of good money. And if the money is not an issue, then just hunt down a nicer looking pistol. There's no real upside here to refinshing it, IMO.
edit: I also concur with the above advice to run some Flitz over it, it doesn't look real thrashed, to me.