As far as I know it is true that the Makila was considered for the 61 in the eighties I believe. The problem however was the gearbox's ability to cope with the drastic increase in power of the makila. We had a incident on a 61 were it landed short and sustained some damage after an engine failure. The incorrect engine was pulled to gnd and when it was pushed forward to regain at least 1 engine, the freewheel unit failed under the load so she ended with a engine failure and a dead freewheel. As is, I doubt whether the gearbox will survive long with a Makila driving it. From what I understood it was abandoned due to the cost involved in redesigning and manufacturing a new gearbox. It does bring the previous 92 gearbox isues to the fore.
I guess with the Makila's and a improoved gearbox, one will have to reevaluate the tail rotor's capability to counter the increased torque? Then the hydraulics and, and , and hence we have the 92 I guess?