Convert it.
It sounds like you really like the frame-- go for it (do NOT paint it, however-- painting original frames is a horrible sin, and in essence destroying a small part of cycling culture; if you're going to keep it, it's your responsibility to maintain it the same way a collector should maintain art).
Converting a bike to fixed gear doesn't break it or otherwise ruin it, as long as you don't remove cable runs, et al.
Take good care of the components and hold on to them. If you decide you want a vintage road bike later on, you'll be ready to go.
In the meantime, enjoy the frame for what it is. Convert it to fixed, ride the hell out of it, enjoy it.

Trust me, the bike will not blame you. If it could talk, i'm sure it would choose being ridden by an enthusiastic rider over sitting in the garage.
Convert it back if/when you get a track frame. No harm done whatsoever.

(oh-- and pics!!)