They should just let people mod the UI freely. The CoH2 UI uses Scaleform, which in theory should be fairly easy to mod; CSGO is another game that uses Scaleform for its UI, and there were a lot of custom UI mods before Valve locked down UI modding. A big problem is the CoH2 UI takes up a ridiculous amount of computer resources; this could be resolved or at least mitigated with lighter-weight UI mods.
Alternatively, they could start charging people for different UI designs and let the community submit UI designs for consideration, like what I feel they're planning to do with decals.
Scaleform is basically flash so it shouldn't be difficult to mod.
I would love to see a minimalistic version of the HUD, and a total overhaul of the GUI as well. The current one looks so dated and clunky.