But...why would you want the tiered system back? To be completely honest, it was fairly unpleasant to have. 6 tiers, with very little difference between one another...even if you reduced it to 4, the same problem would persist. If your wish is to theme the supporter ranks into something entirely different, then yeah, I'd have no problem with that, but it's going to be a mountainous task in and out of itself to decide on things like which Pokemon represents which supporter tier, and which evolutionary line appeases most to the majority of supporters.
At the end of the day, you can't satisfy everyone, this much is obvious. But time and time again having uniformity in colors in the past has proven that people have consistently changed to either their regular user usergroup or basically asked an admin to remove both the userbar and the color and display completely as a regular user. This was especially frustrating for people like myself, who had the supporter bar display at the bottom despite appearing as a regular user, and it'd made for a really ugly postbit.
PC has had a long history of giving people a lot of presentable options and customizations. Now that supporters finally have a chance to pick their own colors, so to speak, why would we change or deviate from that? I personally don't mind the difference in colors, because people would pick what they like at the end of the day and donate that specific amount for it. It's simple, and pisses less people off, bluntly speaking.