^Agree. Most of the worry with the rain is:
a) the bowlers run ups, not so much the fielders. So just put some kind of non-slip matting down over the bowlers run ups so that they can run in at full pace. They'd need to change shoes probably, but it would be a hell of a lot quicker than waiting for the rain to stop
b) the pitch getting ruined. So you wouldn't play in rain for a Test match, but I think you certainly could in a T20 without much consequence and probably an ODI as well.
c) wet ball - just give the umpires some kind of super awesome drying device