Sankaku Channel/

It sounds like a "my favorite tags" system and "my image feeds" are the two slightly different needs the sub system is trying to address in this case.

A favorite tag system would not be hard to provide, the issue is when it comes to letting users actually browse all their tags at once, which is the problem the subscription system attempts to address.

The UI suggestion is very good but I can't help but think there is a more fundamental design issue involved.