Thanks for the suggestions! Your method does seem pretty thought-out.
It all sounds possible, but it is very complex to program because the pathfinding happens over many ticks, so everything has to be stored and retrieved later, during which time anything could have happened (e.g. spidertron deletion, a new command issued, etc, etc).
spider becomes stuck for more than X time (if that can be checked)
Also theoretically possible, but very complex as it happens over multiple ticks.
if possible add the option to switch between "straight" and "pathfinding" (checkbox?) in the waypoint setting, and if toggled, also recalc once.
I don't think there's space in the GUI for this, it is too wide as-is (especially with today's v2.4.0 which adds another button!). I'm not saying that I won't implement it, but it is still low priority, I'm afraid.
It has also been suggested that the spidertron logistics is too overpowered already, and perhaps the 'manual-ness' of the setup helps keep it from overuse :P