I prefer more frays like ACL, BU, & UCL & BR.
These are some interesting combinations that I don't think I'd have considered. It would be interesting to know what others think. From my point of view, if I knew the frays were going to stay consistent like that long term I'd happily invest in them to improve my teams.
I can't speak for others, but from my own experience when coming into the game I loved buying the packs and the specials when the next new release came out, but because I can't buy enough to level up straight away I was still trying to catch up when Rebellion got released. So I feel like most people would be more likely to be geared up with sets that were released next to each other, especially now we have modern in place. I'd envision newcomers buying the current packs and building on them, then either adding in more from the previous release or if the new release is closer building the current and preparing for the next. I could be wrong, though, that's just my approach.
I can understand the wild frays being hard to fill and I think it will get harder as more sets are released. AB was one we struggled with and I think @kiokizz saved us there. That said, our guild player base is now getting older so it's going to be the modern that will be hardest to do moving forward. I believe most of the accounts were playing modern with Cl cards only most of this year. The other hard to fill ones were the max level frays, but recently @ctrph has levelled his wild deck up enough to be doing really well there. I was working on getting U and Cl up to max level as well, but now I'm not sure what to do.
Up to beginner, maybe intermediate is easier to fill with modern, but above that starts to get harder unless you can get a big spender into the guild or someone who loves playing and renting in modern.
My thoughts are that a good mix could work. So maybe Wild, ABU, UCl, ClR, modern
Also, I would agree that GF is a really hard fray to fill and wouldn't be opposed to reducing the amount.