Evolved undead is a special case because it can be applied over and over, so go ahead and make it as big as you want.
As for spell-stitched, yes it should be 1 level long, and I can't see what would be the problem with that. Some DR, some SR, some SLAs, done. It wasn't a deep template to begin with.
But sure, you can go ahead and make a SpellStitched Lord or Greater Spellstitched expanding the 1 level prc if you want. You'll still have to fit the basics on the first level. Making it interesting is the challenge. I've seen 20-level long classes with no interest whatsoever, while other classes are amazing even if used as single dips (cough martial adepts cough).