Were you asking me? I mean that there is currently no (automatic) way of having two sets of anchors: The normal set of top/_top for the singletons, and eg. having Glyphs use anchors called topDoubleDecker/_topDoubleDecker in the cases where a user type in more than one diacritic.
Last time I brought up the topic you never got back on it:
I think I found out a way to answer question 2, by creating a group of all lower-case and all top diacritics.