If you get another scan mission sending you to the same place just do it while you have a bounty, its not a problem flying around there scanning some more with a bounty.
I already do that. I often end up with several at the same planet, so I just go back into SC and back down to do the next one. Only problem with stacking like that is the mission will sometimes fail to complete and you have to do it again before moving on. (Same bug from 2.4, but not as common as before)
In terms of the Public/Legal versions... When I say I have only seen TWO, I am referring to only having TWO presented to me from the mission board over those 7 days. I know the difference. They just rarely come up. And when I say rarely, I am talking almost a "Hen's Teeth" level of rare.
I doubt many ED players have done as many of this mission type as I have. I know it like the back of my hand starting with the original versions, which worked great and paid double of what we get now. ALL but a tiny percentage were totally legal. Then came the infamous bug that allowed you to scan ONE beacon and suddenly every single scan mission you were holding was magically completed in one go!
That was very similar to the recent Skimmer debacle. They didn't remove the scan missions though... It took till the next update for that exploit to go away. It was at this point where the PRIVATE Beacons made their appearance in mass, the rewards were cut by 50% and most of the missions failed to complete after meeting all the objectives.
I obviously stopped playing them until 3.0 fixed the completion problem for the most part. But all the other nerfs remained in place. Including the total flip from Public to Private beacons.