Could anyone design and build a better R22 machine? Possibly.
Could anyone sell said machine in large enough numbers to sustain commercial viability? Almost certainly not...not when someone else - in this case Robinson - occupies the private and ab initio training market so substantially.
That was the gap in the market that really assured Frank's future, and led on to things like the R44, further growth, the refurbishment business he enjoys, the big revenue generating parts business, etc.
Nice idea, though...
Now, where's my sliderule?
Dantruck