In order to compete with Bridge it would be great if you understood the collection feature to be independent (giving it an own database) and not be a child feature under a certain catalog. Or do you want people to use "PM catatolgs" like "Bridge collections"? In fact the latter work but I personally interpreted "Catalog" rather to be a longterm thing and not so much a short-term collection.
If collections were independent databases, how would they be different from catalogs?
Currently the context menu offers "Include/remove" from catalog. If you understand your catalogs as I understand (Bridge's) collections I needed the possibility to add/remove to/from different catalogs as quick as to/from different (PM's) collections. Further I feel that your catalogs are a long-term archive thing whereas collections is mid- or short-term. Private vs. Work photos is Catalog and Xmas 2020 vs Xmas 2021 is collection. The other way round: What was YOUR Idea behind collection when you bound it to ONE Catalog?
I'll have to check with the developers when they get back from vacation, but I believe this was a programming limitation.
My concept of a "collection" is the ability to quickly/easily identify a small number of images to be used for a specific purpose ... such as, I want to select 12 photos for a calendar project. These 12 photos will probably be chosen from several catalogs, so only being able to chose photos from within a single catalog is useless. Creating a new catalog for just 12 photos is silly. I don't need to do name/metadata searches within a "collection." It would just be a quick way to reference a small group of images. I would be happy being able to create collections with images that are not even in a catalog (if that would be possible).
If collections were implemented in the way that they have to be part of a catalog, maybe the way around this is to use a catch-all catalog and assign all of your small collections to the same catch-all.
A "catch-all" catalog would be really HUGE (and would take a really long time to create).
Our developers said it isn't currently possible, but it is something we could look at in the future.