I guess the problem if essentially many game ROM set formats would need to be changed or something to allow this type of "plugin". That would be a huge task to redo hundreds of ROM sets to add that kind of support.
What if the NVRAM file is actually included? I will have to test making an inp in MacMAME 0.60 on a game like ms. pacman I know normally doesn't play on the PC versions but with the NVRAM folder and preexisting nv file there....then copy the nvram file to the PC etc. and try the inp playback. My guess is that won't help but can it potentially allow some games to playback that wouldn't without the nvram file?
Anyway, none of the people of MARP have a Mac? What if a few MARP members that play MAME on a Mac were used to verify each other's inp files? ...like referees specifically for MacMAME inp reviews for games that won't play back correctly with the same version of mame or mame32 on a PC. Obviously we couldn't review our own inp submissions, but there could be 3-4 people and someone else is assigned to view my inp and confirm the score and settings and I review theirs.
Also, is there a way at MARP to submit an inp but not have it publically available? For some patterned games like Super Pacman I wouldn't really want to submit an inp file then someone else can just view my inp several times then just run my patterns and get a score nearly matching mine or surpassing it a tad. It seems all submitted inp files are publically available. This will keep me from submitting inps for certain games to MARP. There are still tons of games though where this really doesn't matter.
Also I think for many games the MacMAME inp recordings play back just fine in mame or mame32.