Personally they should always start off fresh without any or few links to previous Pokes.
If they do want to make evolutions, though I didn't like Scizor, that was a good design. Most Gen 2 updates, Slowking, Bellossom etc were good design wise actually.
Of course Gen 3 only added 2 babies and you can't really go wrong with that, making things simpler is easier than making things more complicated and that of course was the problem with Gen 4.
Munchlax, Bonsly, even Happiny were fine but when you get to the evolutions...did they really have to evolve Magmar/Electabuzz? Of course none tops the terrible Rhydon with a protector, but look how uninspired they were Aipom with more arms, a big Tangela, a fat Lickitung, giant Magneton etc.
If Mamanbou was related to Luvdisc, that would be a great design, again, if it were, and if GF wants to update their older-mons that's the route they should take, not the make-everything-gigantic look of Gen 4. Gallade was done well, and I guess Probopass even if it is ugly as hell, I personally liked Dusknoir but again, it evolved whilst Banette didn't? Anyway I'm OT now so yeah.