... which is why the OP just asked to be able to re-depot the goods.I understand what happened. It's a trap which many people fell into the first time. But preventing things like this can get insanely complex. I mean, the game filters on what your current ship can do.
The general direction of missions has been to let you take missions and refit to take them (that is part of what depots allow), rather than add the guide-rails you talk about. I wish they would add something like the depot to passenger missions - the number of times I turn up at a location, see a nice set of pax missions but by the time my pax ship has arrived they all have magically vanished...