Here is a place to get seat heaters. You could also do the observers seat, or any other location.
http://www.sportsimportsltd.com/seatheatac.html My neighbor installed a shower in his I/O and claims it's better than having a heater. (I'm installing a second heater this winter) He says the Heatercraft produced showers are the best. Of course he uses his boat mostly when camping so a hot shower is a wonderful thing, for him.
I was looking at some pictures of the exhaust and wedge on the Malibu. An FAE is possible. It just requires a couple of extra shallow bends. The downpipe and T section would only require an inch of clearance from the wedge so that portion would be closer to the back of the swim platform than on most boats but you could still do it. It would not interfere with the effectiveness of the wedge and it is really useful for surfing.