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.
Being able to have catalogs of catalogs would be very useful, and could solve this problem too. This would also allow people to have yearly catalogs, and then include them in a bigger catalog that would include everything. Parent catalogs could perhaps even be restricted from storing photos of their own, which might simplify them. This catalog hierarchy could even allow multiple levels, similar to how Aperture had Folders, Projects and Albums.