Okay, well, fair warning - I haven't even touched a line of code in four years, and I never learned my way around the inner workings of data. This is sheerly my geological thinks combined with a bit of fudging. Stop me if this line of thought is straight up not possible. There are huge holes in this I'm already aware of and will address toward the end.
My immediate impulse is: Ditch the sphere, and the polygons.
Here's what I'm going to call a "rock column" for my purposes:
It's nothing more than what appears there - an ordering of rock layers of different varieties (I just tossed out some examples in that image) with their thicknesses. Rock columns could be generated to resemble many different crustal regions, based on what rock layers are present.
A certain number of rock layers (depending I guess on what works in terms of manageable simulation) could be distributed at points equidistant to a point and collectively resembling a sphere (Alternatively with distances from the core varied to resemble real planets' oblate shapes) and serve as rock data for that region.
In addition to the rocks present in each column, they could carry other information - like mass, momentum, and 'horizontal' volume. Their ability to move freely would be constrained when their volumes contact other columns, and in theory that should be at all times. Circumstantially, their momentum may cause them to push against other columns and cause -
A: A decrease in one or both columns' horizontal volume (depending on hardness)
B: an associated increase in columns' vertical thickness, and, if severe enough, metamorphism of existing material (replacement of layer/s with a metamorphic rock based on the parent material)
C: 'subduction' of a column, if one is heavier and thinner (like oceanic crust) than the other. This would remove the column from the planet and maybe add dissolved volatiles into the neighboring column's information?
Columns could also 'stick' to each other and separate the way real plates do, to form larger plates, maybe collectively sharing momentum/velocity?
Finally, I think it should be possible to generate a 'surface' over the planet based on column thicknesses, locations, and upper rock layers?
This wouldn't be a solution for more local issues like weathering/erosion, drainage basins, flora cover, volcanism, or uhhh anything smaller than a huge chunk of land. Even mountain ranges would appear simply as single, huge mountains rather than ranges of individual normal-sized mountains. Nor can I guess at how ugly the seams between columns with different rock layer information would have to be.
Am I on a reasonable line of thought?
EDIT: On a second look through the thread, it looks like this is rehashing what has come up more recently. I'll leave this up regardless, but it's less novel than I originally thought