I know that site loading speed and stability is important. But sometimes .Webp isn't the best image format for everyone.
Basically make an option so a member can select his favorite image format to be used in his/her own submissions (.PNG/.Webp/.JPEG/GIF etc..) It should be either set in setting -> misc so it's always used in the member's submissions, or set in each submission simultaneously (A bit harder to implement, but more beneficial).
This is really complicated to provide a toggle, but if a lot of people really see a difference between webp and jpg and want the old formats to remain I will consider adding this. The issue is it creates needless complexity for both the server and the submission form, as well as just requiring more bandwidth. I don't think I have encountered a website that would ask you what format you want your images saved as.