We already had them in random encounters and believe me, it was exploited hard. It could be an addition to current system, but you need to think up concept, that would encourage miners to use public mines instead of these random encounters.
Oh, so it were already implemented. Actually, it would be the most exploited enc. ever. But there may be some requirements for get these encs, such as high OD, a new Support Perk or stuff like that.
Encounters mining in nutshell.
Or a timeout, where you have to wait, because your character get tired.