Hmm. I might like a Ralts, like Wally from R/S/E. Fits the criteria of a three-stage evolutionary line, though it'll need to have a low power move to start with; currently it doesn't learn any damaging moves until Level 6, and Confusion is 50 Power, which might be a little overpowered. Plus there's some room for individuality, as you have the choice to let it finish the cycle into Gardevoir, or use a Dawn Stone to turn it into the badass Gallade. As someone else suggested, Gothita/Solosis might also be a good choice.
I'd also like to suggest Mareep, Ampharos was one of my favorite Gold/Silver Pokes, I liked that it could learn some coverage moves like Fire Punch and Iron Tail (and in Gen 4 and beyond, Power Gem). The Sandile and Aron lines could also be interesting as starters.
I think Dragon-types would be tough to have as starters since they require so much experience to grow. However, I really like the idea of Zubat; the thought of a happiness-based evolution as a starter is very interesting, as it would really encourage players to take good care of their team.