I just starting figuring out how to mod stuff for this game, so changing what you suggested to change is beyond my current skill level. But I do have a solution that I tested and works (incidentally now I know how I will change the resourceful ability to be more useful/interesting).
Basically all you have to do is make a copy of the survey module for your mod folder. Then check out the ancient ability in the the ability definitions file, that's how you model your trigger for rewarding elerium when you survey anomalies. Then look at the resourceful ability as a model for how to reward the player with Elerium. Use them to add the new feature to the modded survey modules and delete the old survey modules so everyone uses them and you are almost there....
One last thing you'll have to do is change what blueprint model everyone starts with so everyone has a modded survey ship instead of the old survey ships without the mining feature (actually, do this before you delete the old survey module, don't want to crash the system). I haven't gotten that far, so you are on your own there, but I'm certain it's doable.
Edit: There might be an easier way to do what I suggested involving changing how surveying anomalies works on a global level. Maybe something in global definitions? But maybe not, as I said I haven't been doing this very long.
