I'd say don't raise the level cap at all cause it adds pointless leveling (there is no depth to it nor is it hard in FFXIV, just takes long) and invalidated content in one go. Heavensward literally killed off all of ARR and made the game start all over as if it was 2.0 again. Put the work into creating a multitude of content to work toward beating so we aren't stuck doing 2 dungeons for 5 months. Put the storyline through the content as well.