hi rod..
ive not experienced the same trouble with the main cog coming loose by its self..the newer engines on these are meant to be much more user friendly ..or so im told. plus in the last couple of years they have put a bigger engine in it now.. totally agree with you on the tail gyro..its rubbish and doesnt really work as a gyro..

for the amount of money though he wishes to spend then i can only see this as an option ,well atleast if he wants it only to be nitro ..
im not sure but im sort of guessing that there is a conversion kit to make the heli from fixed to collective .. there is atleast on the electric version i think ..mind you even with this improvement it will never be a raptor..lol