sanctums just opened up to apps last month and fits all your requirements, with a 3-to-1 OOC-IC day ratio and a player-driven, overarching plot. We have several MCU cast members including an AU Bucky, but an OU version would definitely be welcome! Peter would be a good fit too, I think. We're super backtag friendly.

You can check out the details on the mod journal @contagio.