A few additional notes on this topic.
First off, here's a notion that Quantopian might entertain:
"IB Proprietary Trading Group Separate Trading Limit (STL) Account Master User. Proprietary Trading Group accounts provide institutions with the flexibility of trade execution, clearing and prime broker services all within the same account. As the Master user in an STL account, you set up individual accounts for traders or strategies with separate credit limits."
Perhaps the Q could create an STL type account and allow funding challenged quants to deposit smaller amounts of capital into individual subaccounts within the STL. The Q would manage these accounts just as a prop-shop might do, as separate accounts with their own restrictions and boundaries. I'm not sure of the legal status of such a setup, but it appears the trading infrastructure is in place to handle that side of things. The representation and tax side of things -- probably a stickywicket there.
Secondly, it appears that there are reduced account minimums for alternate account types: straight from IB site: Required minimums
Category Required Deposit
Individual Accts (unless listed below) USD 10,000 (or non-USD equivalent)
Trading Group Masters USD 10,000 (or non-USD equivalent)
Broker Masters USD 10,000 (or non-USD equivalent)
Indian residents 2 trading with an IB India account INR deposits only, equivalent to USD 2,000
Indian residents 2 trading with an IBLLC-US account USD 5,000 (or non-USD equivalent)
IRAs 3 USD 5,000 (or non-USD equivalent)
Individuals age 25 or younger USD 3,000 (or non-USD equivalent)
Advisor and Broker Clients USD 5,000 (or non-USD equivalent)