How about giving new accounts 14 random champions so they can be eligible for Draft Pick. Then the standard PBE mode can be Draft instead of Blind Pick. We'd get to test more features (banning, swapping), get to at least counterpick to have decent matchups (more interaction/fun/testing), and everyone would have a few more champions they can test.
That or set up bundles specifically for PBE so we can use the RP we get for different selections of champs. I know we can buy bundles as it is, but one of them gives an XP boost instead of bonus RP like the other, so it's not really worth it, if we're trying to test as many different champs as possible.