Hello!
I've been trying to add deck builder improvements as I can, so it's nice to see what people are interested in.
Deck status: We've got some features in the pipeline around "Wish List" decks as you call it, so I think we're on the same page there. We currently don't have any plans for a higher tier of favorite. Although I can envision how it might work from a UX perspective, I don't expect it to be a priority for us any time in the near future.
Deck number: I'm not a server programmer, however, I'm pretty sure it has nothing to do with storage but with server bandwidth. The game is server-authoritative, which means we don't store any information on the client. So every time you ask for your decks we have to send you all of them. I think the current number of decks is designed not to take down our services if people are making lots of requests. (more basically, if people ask for too much data at once we end up DDOS'ing ourselves) On top of that, our deck manager UI would have to be refactored, as it already slows down when you have max decks. So in general, this is possible, but not as simple as changing a number. I'll try to brainstorm what other solutions might help our "brewers" maintain their list of cool decks.
Better filtering: Currently you can sort by alphabetically, last played, and last modified, and you can filter by color and format. Are you interested in a "sort by color" or a "sort by format" option?
I'll keep an eye on this thread for other suggestions. Thanks!