Why reinvent the wheel.
When Bell wanted to upgrade the old 212 and give it two extra blades two rules applied I think. The easiest and the best cost effective solution, from that virtually nil maintenance costs between overhaul and a bullet proof design. The answer was as indicated. Additions to the original design to include the droop restrainers and the pendulum dampers went a long way to solve problems that became evident in service.
Ok so it can be a bitch to track and balance and if removed rarely returns to its original settings and generally needs a few tweaks to get it back to its previous ride.
The old girl is now in her twilight years and not really worth any fundamental changes to her running gear. A shiny flat screen display or two, improvements to the AP and a better power margin doooo quite nicely thank you.
Outhouse.