Priority #1: cost per kWh.
Priority #2: longevity, because it directly relates to #1 via DoD / required pack sizes to minimize cycling.
Fast charging comes in at #3 or #4, depending on where you place safety (since safety issues can be somewhat ameliorated by smart pack design to contain cell failures). But at least it's above energy density, which everyone focuses on for some reason. Particularly gravimetric energy density, which is the least important aspect of batteries these days (it's volumetric that determines how many you can put into a car. Weight is not a problem with today's li-ion vehicles; it'd be nice to have them lighter, but it's not that big of a deal).
And of course, having a high ion mobility on its own isn't enough to have a fast-charging EV. I mean, it's great for cell phones, but with cars you have A) serious supply issues, and B) serious heat dissipation issues. They're certainly addressable, but it requires serious engineering work that doesn't just happen overnightþ