Turboshaft

Half-baked.

A tin can turbo shaft. I've seen some tin can jet builds. I'd like to do that with a turboshaft. I like the designs where the compressed air is used to cool the combustion chamber, which also pre-heats the air.

Output to a belt system. One component would be a motor/alternator. This could be used as the starter motor, but once the system was self-sustaining, it could be used as an alternator.