I joined LessWrong at age 18, and noticed no massive hurdles apart from not having read enough math to comprehend the math-ier sequences, but I can see where you're going with this. I'd have been incredibly eager to start thinking better at age 16 or so already. I would LOVE to introduce my more intelligent friends to this, but it can be pretty terrifying here at first. Your idea sounds perfect for that purpose. I'll join that other site too, and provide feedback if I can.

Edit: Ah, must've skipped a paragraph. Not interested in skipping college, ignore. I'd just be interested in, as with me, casual refinement beside my normal education, as for the people I'd recommend this site to.