If you have access to the desert you could pick up a Trapinch for an eventual dragon type. Numel and Torkoal can both be caught from Fiery Path fairly early too, if you want a fire type. Makuhita might be a solid choice too and he can be found early on in Granite cave.

You've got decent HM coverage already between Wingull, Lombre, and Mudkip so personally I'd replace Zigzagoon with someone else. But that's just me.