Let me laser down asteroids! is a mod that allows laser turrets to be used for space platforms. It reduces asteroid resistence to laser damage to a reasonable percentage for each tier (size). Energy consumption and power generation are, of course, their main drawbacks, and it's up to the player to figure those out.

I don't believe a 90% reduction for laser damage, on a medium asteroid (!), is a good mechanic for a sandbox game. Let the player figure out their own solutions to the asteroid problem.