Phil Bleazey will be the best person to answer these questions, my take from having benefitted from Phil’s experience is as follows -

1) no they haven’t they appear to be happy with the prospect of engine removal as the only way to maintain the coupling
2) the grease reduces friction which occurs as the coupling locks up, this should help reduce break up of the surface of the inserts
3) the existing coupling is designed to be maintained in situ but MMC have put it in back to front and totally enclosed it, Phil’s mods correct their error by putting the removable retaining plate at the clutch end of the drive and then access is provided via a hole cut into the bell housing.

M3W Brooklands (2015)
Moody 41 (2013)