This is a really great product! I'm 5 session in to a new campaign using them and it's working out great so far. Also, I really appreciate the design notes both as a play aid and just genera interest reading.
I do have a couple of questions about how the Seeder is intended to play. First: is the "mine" tag intended to imply that the mines do not arm until the end of the seeder's turn, like player mine systems? Or is it intended that a Seeder can toss out a mine and immediately gravity gun pull someone to detonate it with their second action?
(Doing it with just one mine feels pretty fair and I don't particularly mind; Speed Deployer would appear to allow you to drop three mines in an arc and then pull someone into the middle to detonate all three immediately, which is pretty nuts; I've instinctively forced myself to space the mines out to cover more ground instead of concentrating them this way)