Suggestions for particular beliefs and theologies have been suggested here before. The problem is if one group gets one, then the opposing group wants one. And then people with other beliefs want their own section. Before you know it you have countless requests for every little thing.
I've been on a site like that. They tried to cover so many denominations and the site was so cluttered and hard to navigate. Everything was so separated that there were hardly any people in each of the denomination forums because only a small number would go in each one. The forums were huge, the site was mostly dead.