Just a quick point
A reply to the original post: I was under the impression (having operated the DHC8 for 2 years) that a turboprop is driven by a gas turbine engine! Surely this is completely different from piston driven A/C?
Therefore why need to worry about how fine the prop is? Once the engine has stabilised what's the problem, except possible ice ingestion?
Also the idea of a prop brake sounds great!! No real need to worry about when that dreaded GPU will arrive!!!