An official exFAT package by Jolla, supported by Jolla and available in the official Jolla store would be as good for me as pre-installed exFAT. No difference. (It'd be like a lot of the Jolla core apps today that aren't pre-installed.) You insert a µSDXC card and the system prompts you to either re-format it or install exFAT from the store. No problem as long as Jolla keeps its promise to support SD-cards above 32GB. I'm not sure if MS licensing policies allow "exFAT on demand", though.