Are you planning to have only the two clans? I'd be quite interested in this, but I think the story could get a bit stale with just the two very much opposite clans. If you want I can send you a PM and we could work on ideas for a third one. I'll still probably throw in a character either way, but my interest is definitely heightened by options.
Their level of sanity. Most people won't be insane, but some characters (A tortured artist type, or a researcher that had stumbled on some minor Mythos lore, ect) may have developed some form of mental problems.