An interesting idea. It helps illustrate, though, how hard it is to come up with a rule when you can no longer rely on good faith. Right now there are something like 200 nations in the world. I think that there are currently 104 members of JTC1. Finally, there are (now) 38 P members of SC 34.
So that means that more than three quarters of the world is not currently a member of SC34. At 3 members a year, it would take on the order of 60 years for everyone else to be able to join. Of course, that's the extreme case, but right now most of the third world is only starting to get involved in standards. Such a rule would entrench the old guard, and limit the access of new nations as they seek to gain equal parity.
So it really is quite tough. One rule that occurs to me that might be helpful in the current case would be to have an "unwind" provision that would retroactively invalidate the vote of anyone that upgraded or joined within the last six months and didn't vote more than, say half the time for the next three months.
Needless to say, everyone's better off if the need to reform the rules didn't exist at all. There's no substitute for good faith. But the real world is the real world, and I guess that's why laws and rules exist.