I think starmade would benefit IMMENSELY from having SE style planets. One of SM's best features is it's scale. If you wanna make grand space ships you can and it doesn't even have that bad of a performance hit. SE doesn't allow that. Now imagine planets as large as SE's, where they have actual ground where land vehicles are actually viable. Now imagine that much room to play with with SM sized structures. It would be absolutely glorious.
It may not happen, but goddamn if we could get actual honest to god planets like SE it'd be one of the best editions to SM ever.
Ground vehicles aren't actually viable on most of the landmass of the SE planets... the stock planets are too bumpy for the most part (IE, your wheels will just fly off for no reason), so you're still stuck using either low-altitude skimmers or multi-role support craft (hydrogen powered surface to orbit craft). I'd put together a mobile factory crawler while waiting for planets specifically to make use of vehicles, and I have yet to find a chunk of land where it'll even fit.
Though I will admit to a bit of "what the fuck" when I landed a corvette on a planet in StarMade and... the front and back hung off the edges of the continent.
That said, much of SE's performance hit doesn't come from the voxel terrain as much as the deformable voxel terrain. No Man's Sky has been referenced in this thread--but you can't actually deform any of that terrain, so it's just a set-piece model; at least in what little promotional content has been released.
I can't see that working as well when accounting for destructible terrain (which they'd "need" as a feature of the planets "because reasons"), as planet rendering is already buggy as sin, and then something with destructible voxels would... probably end up with even more of a performance hit.
That being said, if it could be done right and work? I'd be -all- over that. I love building planetary bases in SE (as buggy as it is), and with the options of certain types of doors and other features that won't explode when I use them remotely? Even better.