So far it looks like IB is the only broker that offers this type of an account. The good thing about the IB F&F account is that you can trade many accounts like a pool even though all the accounts are separate. I'm looking for other brokers that offer that.
MB Trading has their MAT (Managed Account Trading) where you can have multiple accounts linked. I have 3 linked that includes my account and accounts for friends that I trade.
I suppose you could use api for each acct if brokerage offers you access (just ask, most platforms do have this) and then use some kind of account copier tool. Perhaps have a coder make a custom tool. Some do have multi-account managers, but may require you to be a funds manager or CTA or something like that. with metatrader 4, I know there are 3rd party account copier tools.