It's similar to the question of "Assuming balanced effort-per-reward, so that players aren't obliged to simply swap to the highest output for what amount of effort they're willing to put in... Should SMN have a higher skill ceiling?"
One approach says that every job should have a pretty high skill ceiling, and people should be free to optimize as much or as little as they like (just give them everything). The other says that each job should have a different skill ceiling, but have their output ceiling vary accordingly, so that whatever they're not interested in dealing with is out of sight and out of mind (customize their gameplay to just their preferred slice). [The third choice is just to have intentional imbalance, as would affect the largest group of players, rather than just the occasional far easier job being less than ideal for speedrun parses.]
Here, too, you have the choice between customization allowing for varying amounts of complexity (which then, if balanced, affects output ceilings), or simply different types of complexity. But regardless, you're still saying, relative to everything that would seem fitting for, say, a BLM to have access to, you're taking only a part of those remaining prospects. More is designed than can be used at any given time. [This is much like how we can't use the kit of every job at once; jobs are, themselves, customization, after all. But here you're now taking a segment of a segment of available gameplay -- an increasingly narrow part.]