MembershipType search changed in 4.6

I'm dealing with a customer report that using CiviCRM with Multisite in 4.4 they can search by any membership type in advanced search but in 4.6 they can only see the membership types for the domain. This is problematic because in multisite (which is the primary way the domain concept is used) the users of the 'parent' domain should be able to get an overview of all memberships.

I'm trying to come up with a sensible proposal for how to deal with this but a few notes

Membership & payment processor have always been the most problematic aspects of multisites for 2 reasons

1) there is a bug whereby if you edit a contribution page or even with a processor you don't have access to or a membership type you don't have access to you potentially save it without that type

2) It actually makes more sense for these to be an ACL in many cases than a coded domain restriction. This probably applies especially to membership types. I would suggest that if an ACL type approach is used it would be up to the multisite module to implement - but core would still take responsibility for saving the domain_id.

I also note that on the other side we are getting requests for more filtering on other entities. This is less about permissions than clutter & covers a range of option values - described to me as "In particular this relates to tags, emails, events, contribution types, etc. – really all lists I think except groups". I think emails is email option lists.

Once again my preference is to think about an ACL type approach - probably via the new basic_get api proposal