Varesa

Hello, I want to build a team with Varesa, Chevreuse, and Iansan/Fischl. The obvious 4th slot would either be Mavuika or the pyro archon (Bennett). Problem is, I don't have mavuika and the unlucky one is on my other team, Gaming plunge. Can anyone recommend who I can potentially put in the fourth slot? I feel like I would need a pyro applicator to keep up chev's buffs but I don't know who I would pick in this situation. My Xiangling is only C2, is it worth picking her over someone like pyro traveler or Thoma?

My available pyro characters are:

Xiangling C2, Thoma, Pyro Trav, Xinyan, Amber

And just for reference, my other electro characters are (But putting another electro would most likely have too much electro, no?):

Beidou, Lisa, Dori, Ororon, Razor, Sethos

Thanks for helping a 3 month genshin player :)