I may be wrong, but I think that there is a large log-in queue because the amount of people trying to access the server is much bigger than riot would want. A lot of people are logging onto the PBE, not to help with bug reports and testing, but rather because they want to be the first ones to try the new champions and/or items. In my opinion, Riot should make it that in order to keep an account on the PBE, people should HAVE to send in bug reports/feedback/etc. If an account is going online, but isnt sending in bug reports/feedback/etc., then it will either be sent a message telling them to do so, or just banned, (up to riots discretion). This way the PBE will only be used for what its meant for.
I may be way off on the actual purpose of PBE, but this is my idea.
Also, again its up to riot, but I think people like Stonewall008 (only example I could think of) should be allowed on the PBE, because they're not going on the PBE for the sole purpose of personal gain, they are also helping the community. (in a way)