the moral question was about them being slaves. What if they built thousands and thousands of Datas and let them make their own choice about whether to join Starfleet or not? That solves the slavery issue by having them volunteer.
In any case, sentient holograms are probably cheaper to make than androids. "Voyager" already pondered this question with the EMH in episodes and in the first few post-"Endgame" Relaunch novels.