Seems I was rather excessive with the time-to-strip proposal - the goal of all these requirements was mainly to give players who stand to lose planets that they would otherwise colonize a chance to prevent the planet from being destroyed the 10 minutes was just a seat-of-the pants estimate of how long it would take to cross 5-7 gravwells.
Now that I think about it, it seems almost like the strip time should be proportional to map size - on a small map, it wouldn't take to long to respond to a strip attempt in your region of the map, but when there are 50+ gravwells, it becomes much easier to find planets on someone's section of the map that they can't reach in 3 minutes or so - making it easy to deny their future economy at no risk unless time-to-strip is increased. Once the map has been colonized, stripping planets becomes harder, so it makes sense for a tech to be available then that reduces time to strip (besides labs, a requirement for many prereq techs would also help keep it from being available sooner).
Regarding any siege damage at all cancelling the strip, consider this scenario: Vasari Loyalists have a titan+fleet, and are stripping a planet. Advent Loyalist have a titan+fleet, and they want to stop them. If they need to siege the planet all the way down to do this, those ships aren't contributing to the fight, giving the Vasari a significant edge. Not building siege ships would mean the Strip succeeds, and they still are facing a roughly even fleet. Thus, the requirement that the Vasari must prevent siege from reaching the planet at all, either directly or through deterrent value (any capitals moving in to siege eventually get sniped by Assailants). Perhaps this is an overreaction, since an midgame Strip-using Vasari would have needed to sacrifice some fleet to get the needed research - but then, they could have sacrificed a few of their own planets to get the ball rolling.
The cost-to-Strip was proposed because right now, initiating Strip is practically risk-free - at worst, you lose the ninja-colonized planet you didn't intend to keep anyway. The OP stated that the cost would be added to the return if you succeed - it just means that if you use the ability near enemy territory, you might actually lose something significant.
Also, I agree that Shipboard Labs needs a nerf as well - don't think the devs intended for research tiers to become meaningless halfway through the game.
Thanks for the feedback!