For example I plan on making a Nord character, that only joins the Companions. Before starting Proving Honor, complete all the quests in Whiterun hold, Falkreath hold, and the Reach. I aim to add more length to the Companion questline due to the quick advancement within the guild, it only taking two or three quests to join the Circle. However, once I becom Harbinger and completeting all the quests within every holds, this leaves only raident quests for my character. I don't plan on doing the main quest besides Dragon Rising so dragons spawn and I don't want to be a thane. I thought of retiring the character after he becomes harbinger, but why end his story there? So do you guys have any ideas to keep a single faction chracter fresh?

I do this all the time. No point in rushing through the faction.

like with the companions. Now I use the Enhanced Companions mod which has set requirements I must meet before the next event will trigger. So Proving Honor for example will not happen until I have reached a certain lv in defensive and offensive skills as well as having been part of the Companions for X amount of days and done X amount of jobs for Aela, Skjor, Vilkas and Farkas.

I don't know of other mods like this for other factions so I make up my own. Example with the thieves guild I do a bunch of jobs between the faction quests. By the time its all over, I probably only have a quest or two and the whole guild has been fully restored and I am appointed the guild master.

Or the Dark Brotherhood. I take on jobs until there is none and then tackle the next faction job.

I even do this with the MQ, learning word walls before proceeding with the next stage of the MQ. Gives me a sense of development and study as opposed to simply just doing what I was told.

I'm on the Xbox 360, but the idea of incoporating X amount in skill levels per advancement is a good idea. Perhaps questing should wait untl after Proving Honor, due to it being mean't for a low level character to be fully recognized.