..upgrade the 120 . . more power . .
They have already. They call it a 350B2. All the power you need and they throw in an extra seat as well. What sort of power did you have in mind?
I recall seeing a similar question a year back where the writer wanted an EC 120 with more power, bigger M/R blades and a higher MTOW. Kinda gave you the idea that he actually wanted some other helicopter.
Seriously though, the 120 has 510 SHP with some 430 allowed thru the transmission. It might be better to wish for a higher permissable Tq. You ever tried to top one out and keep within the Tq limits? You'll be way up there before it droops.
I guess that if by some miracle an additional 100 SHP came on line, then there would be a chorus of "When are they going to increase the MTOW?"
STL