I think the real solution has nothing to do with proxies...and it may not even be a matter of the reserved list. Sure, it'd be great if power was cheaper to acquire, but there are plenty of people that could do it and don't, yet pay big for Modern and Legacy. The biggest deterrent I feel is prize support and frequency of high-profile events. If you could pick up a playset of goyfs, bobs, seizes, chalices, and other pricey cards to play a BG rock deck, or a set of blue duals, FoWs, and other junk for Legacy, you're not far away from chipping away at pieces of power.
But why buy Vintage cards? You can go to lots of Modern tourneys and some big Legacy tourneys to a lesser degree - but when are you ever going to use that Vintage deck? Once or twice a year at best? And for what - a $100 entry for a shot at winning an underground sea? Cmon.
Vintage is by far the least supported format with few "big" events and usually crappy prize support or something decent but for $100 entry. If proxies were allowed, people might get in more easily and try their luck...but nobody is going to invest all the way for a format you rarely get to play and for low EV in prizes. Us old folk who bought in early and are now near 40 are the bulk of the scene. We can't expect young players to come in if the opportunity to play often and for good prize support isn't there.