It sounds like he needs the funds for trading. I don't think escrow would serve any purpose for this.
I liked idea with escrowing money in 2-of-3 multi signature. This is more reliable than having all BTC at Bitfinex.
Don't worry, I have 930USD at Bitfinex at the moment ( check yourself - account is public ). My margin is never more than $300. When I will have $3-5K under management I would buy more BTC to satisfy trading size.
Currently, I'm the only investor and I have enough margin for my size.
Edit: updating funds custody section