Adorable creature. The solid color one looks striking and cool, and little chibi version is particularly cute.
John Castaway has its own merit for being closer to TF2's art style, but anime mascots are just way more meme-able and interesting to look at. One thing I'd suggest is to simplify her chibi ...

The idea of having Castaway's own map (or map edit) sounds interesting (as long as it provides some actual objective-based gameplay too), but starting every session on the same map sounds terrible. Probably not the best for attracting new players too.

Weebs are the most numerous yet the most oppressed group on Castaway. How long can this go on?