Yes it's true that there is no free lunch, but I understand what is trying to be accomplished here. I have looked into this somewhat. I know that I originally heard about this concept awhile ago from a traderinterviews.com guest. I don't remember his name, but all of there interviews are archived. He said that he bought the spot fx and sold the deep in the money call against it. This would enable him to hedge the price risk and let him earn the daily interest.
I don't think he mentioned which forex broker offered the options however. The problem is finding good forex options to trade. I have read to many horror stories about forex brokers screwing people on the spot price side alone, let alone any options.
That leaves the new listed fx options traded through traditional brokers. I have traded the EUI (USD/EUR) somewhat. The interest is absolutely built into it. Deep in the money puts actually can have negative extrinsic value due to the interest that should be paid them. But I think what we are getting at is whether a deep ITM call far enough out would still have enough time value to offset the interest rate differentials. Unfortunately there are only the USD options at the this time. No GBP/JPY or NZD/JPY.
Using the XDB ( GBP/USD). Spot is 173.75. The 167 Nov call (46 days to expiration) has 1.55 in extrinsic value. So you could buy one mini lot and sell 1 call against it and you would be hedged down to 167. Not only would you make the daily rollover, but you would also get the $155 in extrinsic value is it was above 167 at expiration. So it can work. Another good one would be the XDA (AUD/USD). Although today due to the huge dollar rally, there are actually no in the money calls. I have watched this a little and I think the market makers purposefully don't offer deeper in the money calls for this reason. They know people will hedge them with the spot market.
The drawdowns to this strategy are namely the huge margin requirements of selling a naked option. To hedge one mini GBP/USD contract you would need over $3500 in margin. Also the spread on the 167 call is currently a ridiculous 40 cents. Also you will not be protected if the spot price goes below 1.67. Also you will need to figure out how you will close the position, since they will not offset each other. Besides, being assigned on an option at Think or Swim is a $15 fee, which I've always thought of as a rip off, but that's just me. You could just try to roll it over to the next month, but of course then you're paying the spread to both close and open a position.
I hope this helps you.