Bad idea i think.
In essence it means i pay for deploying mines, with the added danger of increasing my enemies income when he salvages them.
Yes, that is the point in fact.
I agree that it MIGHT be a bad idea when it comes down to it. If what you say above cannot be balanced correctly, there is a danger that mines would be obsolete and un-used, because all you do is feed your enemy with them. This would be bad.
However, it is POSSIBLE that it could be balanced correctly (I don't know as I've never tried to do it). For instance, mines could be useful in a system with a fleet, defenses, and a starbase. Your enemy would have to drive you out of the system before he could contemplate collecting your mines, and he could still be counterattacked there while collecting the mines. Mines here seem to be doing you - the defender - some good.
However, consider the case where all you do is run around the galaxy spamming mines in every system 'til kingdom come. It would seem you are just leaving free, undefended resources laying around for whoever wants to collect them. This strat might be effective against a newb, but its a strat that would not "scale" to a better player. So, it seems that this suggestion has the potential to address some of the complaints of the mine-haters. If you are a mine-hater and your opponent spams thousands of mines indiscriminately, you should at that point be converted over to a mine-lover, because your moronic opponent has just given you tons of easy, free resources.
I'm not claiming its a good idea (who knows?), but its certainly an interesting idea. What I like about the idea is that it is "self policing" - the game itself does not have hard limits or rules about how you want to use mines. Rather, there is the possibility that you could be severely punished for misusing them. In general, I find that "self policing" systems are the best systems, whether in games or real life.