Hey Sandro,
As an opponent to instant transfer I am glad you guys are thinking some more about this topic.
Now regarding the actual numbers, although I am absolutely fine with a minimum delay of 5 minutes which sounds plenty believable (which was my main issue with instant transfer beside the gameplay implications), and without really knowing how these will scale with distance, I do feel like 5 minutes minimum might be a bit much for some people. Of course for those only interested in the feature to relocate one big fleet of ship from one home system to another (and thus who probably don't need all of those ships immediatly) virtually any delay would do, but I know there are those who just want to be able to quickly accesss a specialized, low jump range ship. For those players, 5 minutes is both way too short to do much in-game in the meantime, but also probably a bit too long to just wait it out and might lead to them just doing something else entirely.
Now again I don't know how that will scale with distance, it's quite possible that the way you want to implement it we'll rarely wait just the minimum delay and thus might have more time to go for a round of bounty hunting while waiting, or it could be that it will be a lot more common than I think. But with that in mind, personally I'd be also okay if the minimum delay was reduced to something more bearable for those wanting their ship sooner rather than later. My main concern with that change and Michael Brooke's explanation was one of believability and immershun, but I feel like whether the minimum is 2 minutes or 10 minutes, the handwavium is much easier to swallow than if there was no delay at all.
Still I realize that your main preoccupation here is the effects on gameplay, not so much our sense of immersion, and that reducing that timer would bring us closer to those negative effects you mentioned.
Sandro - if we could at least SEE a bulk carrier arriving at the destination station, that would make for another awesome cinematic moment in the game
Doesn't matter if at first we don't see ships being carted to and from it (thought that would be awesome) - just seeing such an event would be nice - although I suspect you don't have the dev time for such - oh well
Give that man the whole jar of cookies!