Rofl.
Can't you just turn it into a RIF once you get it? Remove the paint, repaint it, whatever. Using your defence as a skirmisher to make it legal? You can prove you're a skirmisher without having to be 18, only difference between me and you is that the retailers association can only sell to someone over 18 by law.
We're still both airsofters, so we both still have that as a defence to grant us our exemption against the VCRA. There's nothing in the VCRA that says U18s can't manufacture RIFs out of IFs if they're airsofters.
You just need photo evidence, or a skirmish diary, or junior membership and you're golden.