I'm a big fan (Sorry for the pun) of Not reinventing the wheel and as such I think Rotordyne should be revisited. Whould an updated design of this Aircraft really need Tip - jets?
JF and I disagree (politely) about the Rotodyne, which is often accused of having been 'too noisy'. The first prototype was certainly pretty noisy, but huge advances were made throughout the latter days of the project and considerable noise reduction had been achieved. When it flew to Battersea Heliport, there were NO noise complaints, just a few curious enquiries as to what was going on.
The Rotodyne did not need massive helicopter transmission systems and only operated in tip-jet mode for vertical take-off or landing. For the rest of the flight, the rotor operated in free-wheeling autogyro mode, with additional lift from the stub wings which housed the main engines - another source of programme delay, courtesy of Napiers.
Just as the production version's specification was being signed-off, the much-underrated Rotodyne died under a Conservative government several years before Wilson and his fellow-travellers killed TSR2, HS681 and P1154. A pity; had it been developed than the Rotodyne could perhaps have been a pioneering inter-city airliner and military transport
Nowadays you'd have to find a 'killer application' for the Rotodyne to be resurrected and there simply doesn't seem to be one.
It was certainly more viable than the Do-31.