Quote from Trader/God:
Why would any broker provide you with a way to circumvent their charges while leaving them with odd lots all over the place? The FX market has gotten along fine with out such a silly system in place. If you want GBP buy it, if you want JPY then buy that. So to answer your question, no brokers are going to provide this but if you were looking to break into the market you can make this your niche. You will have very little competition.
Trader/God
If a broker allowed me to do this, I would more than make up for their lost commission through a very high volume of trades. Maybe I need a very large account at a bank rather than a broker?