This is a way to fix all the performance problems related to planetary mining, without having to resort to asteroids.
(Not that asteroids are bad, necessarily.)
Add a "mine entrance" element / core, that you have to place on the surface, and which gives you access to the underground.
Then take away the ability to punch arbitrary holes in the planet (this would require a planetary surface reset).
Any time you're underground, you go through an entrance, so the modelling of the tunnels is completely isolated from anything else in the world*.
Mining then has zero impact on anything above the surface.
(* in theory the code could check if one of your tunnels intersects someone else's, and could join mines together in that situation; that is still a far more constrained problem than the way it works right now)
This is a way to fix all the performance problems related to planetary mining, without having to resort to asteroids.
(Not that asteroids are bad, necessarily.)
Add a "mine entrance" element / core, that you have to place on the surface, and which gives you access to the underground.
Then take away the ability to punch arbitrary holes in the planet (this would require a planetary surface reset).
Any time you're underground, you go through an entrance, so the modelling of the tunnels is completely isolated from anything else in the world*.
Mining then has zero impact on anything above the surface.
(* in theory the code could check if one of your tunnels intersects someone else's, and could join mines together in that situation; that is still a far more constrained problem than the way it works right now)