More of a pipedream here, but I'd rather keep just 3 secondary stats, strip offensive power from Tenacity, and move it, Piety, and some new stat into a separate Tertiary level of materia to compete basically only among itself for cheese stats (such as via Tenacity, Vigor, and Mobility -- to increase both mitigation types, MP and HP gen over time, and movement speed and Sprint frequency, respectively).
VIT, STR, DEX, INT, MND; Will, Speed, Break; Tenacity, Vigor, Mobility.
Would also really like to see Materia be independent from gear and set job-by-job, with no costs to swap (only to extend the pool, if that)... Allow us to set a target GCD speed, crit rate, etc., in ordered priority, with a dump stat chosen, etc., so we can have agency without the inconvenience of constant swapping of surrounding materia with each new gear piece.
(Or allow all jobs to use all stats, and let us actually overcap Vit, and have stats provide a bit more utility value on jobs for which those stats may have a lower scaling towards total power, as to give cheese/safety options at cost to output that way, though I imagine that could get a bit complicated for some despite the huge increase in actual customization and reduction in item bloat and gear grind during leveling that such could futureproof.)