[Sundraoi]

I would suggest moving the feat rather than starting a trend of mechanically enforced "valid" builds.

If you move the feat to 3rd or 5th level, a person is still forced to take X number of levels to get the feat, the agreed upon reason people take the SD class. How is that any different than forcing them to take X levels of the PrC if the feat is offered at 1st level? They are still forced to take X number of levels in SD regardless.