I did not find a previous proposal (but it may have been already discussed):
The upvotes gained on the various meta subsites of the Stack Exchange network do not count for the local reputation and that's quite natural. This is clearly by-design.
The meta.stackoverflow.com is the only SE site where you build reputation by discussing the characteristics, features and bugs of stackexchange network sites.
So, I would find it good that all reputation collected on the various meta sites be added to the meta.stackoverflow.com reputation. You would then have one "meta" reputation across all sites, but local meta discussions would stay local as needed.