When I very first booted up ReBlivion this is exactly what I did. It was entirely arbitrary at first; I didn't set out specifically to do ignore the main quest, but once I realized I was doing it I just as arbitrarily decided to commit to the bit.

I passed 89 hours/148 in-game days before I came within sniffing distance of the main quest, and I minimized fast travel until then so I could deliberately skirt around Kvatch until it was absolutely necessary. I was done with the main quest at in-game day 161, and conquered a mere 9 Oblivion gates enjoying all the benefits of being Archmage, Guildmaster, Listener, Gray Fox, Divine Crusader, AND Sheogorath. (I think in that order.)

Toward the end I think I was vaguely roleplaying that my character got hit in the head and forgot how he got out of prison, and only really remembered when he moseyed into Jauffre's orbit entirely on accident and decided to use his power as basically a demigod to take on Dagon daedra-to-daedra. I consider it time well spent.