I think it's possible, but it would have to be water of tobirama's suiton jutsus. I don't know how it would work with gaara, how does gaara sand control works? Does he put chakra into the sand to control it? Because if that's the case, gaara would be a monster with fgt.I doubt it. If so, then he'd be pretty OP. But imagine if Gaara had FTG and this was the rule on FTG. He'd be unstoppable.