I've always thought that a decent sized outboard on a stern bracket would make a good emergency get-home, or at least lend enough directional stability to work on the main while quartering waves. Trouble is, whatever outboard you get over 15 HP is going to be a darned heavy dinghy engine, so you might need an additional OB for that, OR, get a bigger dinghy to handle the bigger engine. Then there's the extra gas aboard, or maybe propane. An electric 40 HP must be really expensive, probably heavy too.
If I've got to dedicate a bracketed OB for a get home, it'll probably be a Yanmar 27 HP Diesel with the idea that it'll just hang there, BUT, will use my same tanks. A fuel polishing system and maybe a day tank would be the wise thing, regardless. Of course, I'd have to buy it somewhere in the Caribbean as these engines aren't EPA approved for sale in the US. Second choice would be a bigger dinghy and the 15 Lehr from Hopcar. My 9.5 Caribe already squats with the 9.9 Merc.
I've moved my old reconditioned 4.5 Northern Lights/Lugger into a new hatch under the veranda. Another Manatee owner has supposed that I could run a direct shaft off a pto to a foldable prop very easily, but I believe the Lugger 3 cyl. is only 11.5 HP, maybe less. It might be enough for a couple of knots.