Slowrotor, HTP is actually a very good oxidiser - better than LOX in many ways. The only real problem for heli usage would be availability, although it would work well with Jet A1.
I'm really curious about problems which would occur using rotor as a centrifugal compressor stage, either pre or post combustion. Avoiding powertrain complexity for either recip or turbine may have cost and reliability benefits. Clearly nozzle design is critical to keep noise down. The other potential disadvantage is having additional tip mass, both for rotor dynamics and durability (hingeless assumed).
The main reason quoted for dropping tip jets is high fuel consumption, although most tip burners were not designed with noise reduction in mind. Historical development has abandoned the tip-jet, but as an engineer it is my duty to establish whether the problems could be overcome with modern development techniques like CFD.
Mart