When I was building 'Natterer' (see my ongoing build in 'Natterer' - A shipbuilding Oddysey) I built her as a full steam launch, with fully functioning steam plant. However, as she was also my first foray into steam, I hedged my bets by installing an emergency electric drive geared to the propshaft, engaged by means of an electro-magnetic clutch, with a small battery giving about five minutes reserve power. By flicking one switch on my transmitter, I can control both systems.
Now Natterer is big - 6' long - and I had plenty of room under the bottom boards to install the electrics, and space for lockers to hide batteries and electronics, which I appreciate an open launch such as 'Wide-a-Wake may not have. Might be worth thinking about though.
As an added bonus, I found that she sailed so well under the electric motor that I have also put together four 12v gel batteries in a pack that can replace the whole steam plant (which comes out in one piece) and gives me hours of sailing if I'm feeling lazy!
I can also sympathise with your transport/handling problems - 'Natterer' has an all up weight of 80lbs. That's why the steam plant comes out in one - it gives me two 40lb packages, which are far more easily handled.