So this is a new submission idea I have, if you were to export a design/build in Minecraft through a Structure block right into your files, you should have the option to upload it right into Planet Minecraft as a .zip file (Java) or as an MCSTRUCTURE file (Bedrock) rather than having to make a new, blank world just to put your structures there which is much more tedious in Bedrock Edition due to the fact that you cannot edit superflat worlds there to have absolutely nothing.

It should be easy to program since it would function the same as the other submission types, but if some extra work is wanted, the MC world viewer could be adapted to be able to view structure files from the website too, that's just an extra idea I have lol..