I don't necessarily agree that lowering the reputation requirement would be desirable or useful (on GDSE or anywhere else in a similar traffic-disproportion situation).
Any StackExchange site is built by questions and answers. They're the most important aspect of the site. Second to questions and answers is the visibility of the site outside the network (to draw in new users, neophyte and experienced both, to contribute to the Q&A feedback loop).
Reviewing the queues is an important aspect of maintaining a site and to an extent shaping it, but I would argue that if one is really interested in growing an SE site, one has access to all the tools they need to contribute most effectively almost right away:
- You can flag questions at 15 reputation. This is more than low enough, since you exceed that simply from the inter-site linking bonus.
- You can answer questions at 1 reputation.
- You can always promote the site externally via Twitter or whatever other organic reach you may have (word of mouth, IRC channels, talking about how you found a great answer to a problem with co-workers).
Further, I do agree with Shog's point that using the site is the best way to learn how to effectively deal with the review queues. Building the experience of answering (or attempting to answer) questions can help build one's background for why certain review decisions should be made. Why this should be closed as too broad but that is just borderline enough to stick around, et cetera.
For GDSE specifically, what the site needs now is more good answers (and more good questions). It does not need more close votes. Certainly it would be very nice to have more users who can review so we need to make fewer unilateral moderator decisions, but I don't think it's so big a problem as to warrant a change in the software; I feel like that would be treating the symptom and not the disease.