While reading the premise, I envisioned the GM getting overwhelmed at keeping up with 20+ threads. You would definitely want no less than 10 co-GMs, or maybe 1 co-GM per 3 players while you give the basic layout to the co-GM's and answer their questions about how something specific should be handled. And of course as main GM you'd have your own 3 players you'd shadow. The problem with that would be 2 GM's shadowing 2 players who are interacting and something battle-esque goes down.
battles would be another issue, as a 5 minute battle (if 1 day = 1 hour or so) would last 14 or so in-game hours. And if a day was a minute, you'd have to wait a month before posting again if you were walking across the city to the tavern, or half a year if you were going to sit and drink for a few hours. It would be best to ignore time in such a setting as different threads would move at different paces.
battles would be another issue, as a 5 minute battle (if 1 day = 1 hour or so) would last 14 or so in-game hours. And if a day was a minute, you'd have to wait a month before posting again if you were walking across the city to the tavern, or half a year if you were going to sit and drink for a few hours. It would be best to ignore time in such a setting as different threads would move at different paces.