And this is why I can't take you "make ranged great again" crowd seriously. Hypercharge is active for approximately 20% of an encounter and this alone should make you realize how big the difference is between this hypothetical version of MCH and the current BLM in terms of freedom of movement (unless you want to argue that blm is cast-free 80% of the time). Furthermore, it can be used flexibly outside of wildfire windows. The longest you'd have to stay still is 7.5 seconds, which is more or less equal to 3 hardcasted fire 4. If you know a mechanic will force you to move, you'll delay it, as the current nature of MCH allows that. In fact, I'm already doing it most of the times for some reasons I'm not going to explain here. If you think that my proposed solution is too unforgiving and the punishment for moving while using HC is too severe, numbers can be lowered a little so that if you screw up you don't lose too much damage, though I personally like the idea of MCH as a high-risk, high-reward job. By the way, these are rough suggestions that can be easily adapted to make them easier to execute in practice. For instance, in the case of HC, lack of movement can be changed with a "grace area" with a radius of 2y, like a small ley lines, and if you stand there your heat blasts do more damage.
The yalm requirement was made especially forgiving so that it would be easy to achieve without having to place a ruler on your monitor. Just know that max range is 25y, so 10y is less than half of that, and small enough to be able to receive all aoe heals in the game, with the only exeption of cure iii...in which case, again, you'd just have to pay a very small price, go stack with the party, and then go back to the required range. What I suggested is absolutely doable in a savage/ultimate scenario with some planning. All of it. The only possible problem I see is, in fact, with foe requiem, because the game's net code sucks, but even if it took 2 seconds for the debuff to be reapplied it wouldn't be a big deal.
To conclude, do note when these requirements are not satisfied, the job would still be doing damage. These changes would just give something more for those that want to work for them, unlike a BLM or a RDM that has to cancel a cast to avoid a mechanic or a melee that needs to disengage. For them, damage is zero in those cases.