I doubt it'll work. Try it and see.
If you know some basics of 3D modeling you should be able to understand fairly easily: Planet meshes only have vertices on the surface anyway. RandomMesh selects an attachment point from the Vertices the mesh is made of, so RandomMesh would only ever target the surface of a planet. On the other hand, your suggestion of "surface" still includes the opposite side of the planet (which RandomMesh should do too, but honestly I've never seen my anti-planet beam fire "through" the planet)
You (the devs, not you) could write a simple algorithm to calculate the point on the bounding sphere between your ship/refinery and the center of the planet, but I doubt they did, as it isn't used in any stock effects.
If you aren't familiar with 3D modeling please tell me, because then I'll have to come up with another explanation.
Edit: Remember though that if you target Center you only lose the impact effect, and the only one that's even properly visible on a planet is the Vasari bombing one, which doesn't fit your ability. The one from Cleansing Brilliance is a blue cloud. Better add a Drain Planet effect to your ability instead.