Sorry to spoil your hopes guys, but even if the AI will build boarding ships it will never be able to actually steal a ship. How do I know this? Because I have tried to get a good design of a boarding ship to use in sim turn pbem games and it just can't be done the way ship with boarding orders act in strategic combat. There's no use putting shielddamaging weapons on them since they will not close with enemy until the shields are down on at least one ship. But they keep so long back that that ship will be destroyed by your regular warships before they get there to take it at which point they will move away again. So the only way to be 100% sure you'll be able to catch a ship in strategic combat is to have one ship design with shielddamaging weapons and one with the boarding parties. But they better be able to take a serious pounding from the normally armed enemy ships. If you get the AI to do that I'll eat something distasteful.
The basic problem is in how boarding ships operate when under AI control. If they where muche closer to the action it might work. Or if you could somehow tell your regular warships to pound down the shields on a juicy target and then
stop firing to let the boarders do their dirty work. As of now I don't think you can.