Hi
@toby_shaw and welcome - impressive website and amazing builds!
Proposals aren't limited to the ideas list so yeah if you'd like to work on something more creative like in-game content creation that would be an option too
Two other ideas to mention real quick that may fit:
In the past we've talked about having various editors in-game. We already have the behavior tree editor so it is certainly doable
We also used to have some blueprint / copy-paste options so you could place structures copied from one spot to another. But that was in the legacy version and not carried forward yet. Not difficult, just a big game with only so many people working on it. Maybe since you have so much experience with big builds it would be something to develop an in-game (or even out of game via world editors and such) ability to store builds or components for later reuse in some catelog, or even a custom block editor for miniaturization (build big thing then shrink into a normal block to make that custom block available normally) or creature making (embedded mini-Blender like VoxelShop).
Lots of options but yes grab the source and play around with it some to get started