SJ:
If I remember correctly, someone on this forum somewhere (don't you just love how specific my answers are?) had decent luck with ship/planet captures. The way they did it was to set the
fleet strategy to the corresponding "Capture" strategy and set the ships to
NOT break formation. That way, they all follow the fleet strategy. You also might have to give the capture ships a weapon (not sure on that one though, see below). I can't remember what they set the secondary fleet strategy to, but the general Idea was that every turn (or whatever frequency it occures at), the AI attempts it's primary strategy and tries to capture. If it can't, it reverts to the secondary strategy and proceeds to pound on the target. This cycle repeats until the primary strategy
can be achieved (by the capture ships, anyway); at which point they rush in to attempt the capture.
You might have to give the capture ships a weapon (I think shield depleters were the favorite) so that the they will stay close to the combat and be in range to attempt the capture. Any ship without weapons automatically reverts to "Don't get hurt", IIRC. The same problem exists for PDC support ships. PDC isn't considered a weapon, so without a weapon thrown in, they just run for the corners. However, I
think that the "don't break formation" overrides this, and the capture ships stay in formation anyway. I can't remember for sure, but this shouldn't be hard to test for yourself, anyway.
Note: If this works for capture ships, it should also work for PDC ships. IIRC, there are two entries for ships in the break formation menu: with weapons and without. So theoretically, you could set the ships with weapons to break formation, but the ones without weapons to stay in formation with the leader. (I think the leader has to stay in formation as well, so you may have to set a PDC or Capture ship as the fleet leader. Or I suppose you could make the repair or supply tender the leader, although I don't see why you would want to....
)
Anyway, that's just my overpriced $0.02...