I notice that between games (notably between Rescue Team and Explorers), despite there being 350 species of Pokemon to choose from and beyond, they reused a lot of species for multiple characters that are rather different from each other. Which to me, kind of lessens one of the two as the one that will no doubt be forgotten to the sands of time. Some make sense like Kangaskhan and the Kecleon Brothers since they always fill the same role, but others end up being completely different sometimes.

For instance, we have Wigglytuff the Guildmaster, and Wigglytuff the owner of the Wigglytuff Club where you buy friend areas. There's Gardevoir the victim of the Ninetales legend, and Gardevoir the member of Team Charm. Same with the Medichams from both Team Meanies and Team Charm. There are Diglett and Dugtrio the father and son pair in Pokemon Square, and Diglett and Dugtrio the members of the Wigglytuff Guild. And of course, lest we forget Xatu the seer on the Hill of the Ancients, and Xatu the owner of Xatu Appraisal in Treasure Town. And I'm sure that's not even everything. Why reuse these species when there are so many others they could have dipped their fingers into for the first time?

If you were given the task of replacing one of these two doubles with a completely different Pokemon for the sake of variety, which one would you replace, and with which species? Or, would you even do it at all, and if not, then why?

Bonus: If Pokemon from the same family tree as a potential starter fall into the same "doubles" category (Grovyle the Thief, Charizard from the A.C.T., Persian from Felicity Bank, all of Team Hydro, etc.), given that your starter can eventually just straight up become one of these later on, see if you can find any worthy substitutes for those as well, or again, argue whether or not they even should be replaced.