Having given the Spider mine a good test this time through I found them to be really great now, however, there is one thing that I think should be a possibility for an upgrade feature.
1: You should be able to purchase (research) an upgrade to the mine so it can move through GOO… have it covered in some kind of silicon skin so that it is no longer stopped by GOO
2: this could be a purchased upgrade or a research ability, just like it is for the legs.
Because the mines become expensive and useless once they start getting the goo attacks…
This would make them perfect!