Blue D. truncatus were actually near the top of my list before I even started thinking about working with frogs that are less common. I asked in the local thread but no one seems to have them, I had read that they were less common, but I didn't realize just how uncommon they really are. I wish you the best of luck expanding your collection, I'm sure you have a mile-long waitlist, but keep me in mind if/when you have some groups ready, I would love to be part of keeping the species in the hobby.
I think that focusing on a species is a great idea. I was going to try to get all the D. leucomelas morphs, but now I'm thinking of trying to just keep a few species/morphs and try to learn as much as possible about the few I keep. I really like your Zarayunga, I hope you keep having great luck with them.