The first gen Insight did something like you're talking about (exhaust heat recovery) by the simple expedient of having the exhaust manifold cast into the head (and water jacketed).
I guess the way I'd go about it would be an electric coolant pump teed off one of the return with the output teed in on the intake side. Feed it to a length of copper piping wrapped around the exhaust manifold... seems like it would speed heating up a bit.
Pierburg Cooland Pumps CWA 50 $75 - DIY Electric Car Forums