So, I want to create a mod that supports older versions of minecraft with the new GUI, but I can't because of how MCreator works. So, how about, in a future update, there is a way to select what version of minecraft your mod is for.
For example: when you create a workspace, it will say "What version(s) of Minecraft will this workspace support" with a dropdown list that contains versions as old as forge suports to as new. (From 1.1 to 1.8.9!) This allows for more flexible mods for modpacks (Because admit it; You don't see many 1.8.8 modpacks). I think this should be added later on at some point.