I don't mind a ranking system where people are given the BP system without a way to replenish it outside of timer. Just do your rank quests and score as high as you can then proceed to relax while it fills up. A quest mode for such system could be something like 'endless Survival' where you are fighting endless waves of enemy and you're scored by which wave you lost at. Sure, money spenders have it easier but a good player would be able to proceed further since they'd build their team much better. Heck, modifiers could also be added every start of battle which debilitates the Servants so they can't do cheap nonsense like Double Merlin NP Bonanza. One wave could induce NP Seal for that entire wave and another wave could induce a Skill Cooldown Extension which causes skills to have extra cooldown time on it when used during that wave.