Easy Way to Improve the Coliseum Experience
Firstly, I'm not a big downer on the new update. I see the downsides others have pointed out, but as a [mostly] F2P player I don't really care about the monetization of Coliseum and the issues whales may have with it.
But I do have a suggestion on how to assuage some of the issues that came from segregating era characters and progression from our main rosters. It's actually fairly simple: unlock all new era marquees at 2 or 3 stars at the beginning of the era and let us upgrade them to theorycraft which teams work better for which bosses. Preferably, there would be a mechanical incentive with the boss encounters to continue bringing up each of the 6 new characters to remain in par with the others.
You can still run the marquee events and era challenges on schedule. You would need to round out the scaling for era resources to upgrade each character, but that would probably make things simpler for CG anyway. It'd certainly decrease the silly moaning from the player base when seemingly out of nowhere the episode chest decides to multiply the amount of currency it gives you.
This change would give players a chance to theorycraft with new marquees and have more control over their game experience, all without having to overhaul the new Coliseum/era system. Think about it, please.