The only guilds that I've ever risen to guildmaster (well, Patriarch, in my case) status in would be the temple of Akatosh, and even then because one of the required skills is Running, which is one of the easiest skills to develop (I had 100% by about level 9, with it as a miscellaneous skill). So that probably counts as cheating in some obscure way. I never have trouble with getting reputation in a guild - it's the skill requirements that restrict me. I didn't notice any particular benefit to being Patriarch - I didn't notice any special Patriarch quests nor any benefits such as new services in the temple. Apparently, for every new rank within the Akatosh Chantry, fast travel time is reduced, but if so, it must have been a minor reduction. I used the temple as my sole source of quests for that character, so I was doing quests fairly often and thus had a constantly high reputation, but I don't know if you actually need to do quests. But I don't think you can be demoted - only kicked out if your reputation goes below zero.