Welcome to the Community Forum. 
I’ve experienced the ear issue you are describing (and have seen the doctor) several times over the last couple of years. For my part, I opted to use a full-sized headphone for a part of my listening – mostly the part at home, as I still use my Fairphone TWS earphones on the road (walking or on the bus) and I find in-ears still give a more immersive listening experience. I just don’t use the TWS 100 % of the time anymore and try to go for the on-ear option more often.
I doubt that Fairphone would present a third option in between the Fairbuds and the full-size Fairbuds XL. By the way, if you want the company (Fairphone) to know, you’d need to write to them directly, as this is a forum mostly run by users for users.