A simple solution to combat all the cheating!

[Packetdancer]

Or in pvp where people use cheats which you can also detect through the log cause no human could switch between multiple targets in mere seconds to killsteal etc.

While in essence I agree, this one thing I feel a need to correct you on: it is indeed possible to switch targets around very fast as a human. Specifically, you can bind the party list, enemy aggro list (or opposing team in CC, as it is treated internally as the enemy aggro list), or even the alliance list (though that gets wonky) to the mouse wheel, right in FFXIV's own input settings and keybindings.

I have the mouse wheel (on its own) bound to scrolling through the enemy aggro list. If I am tanking and someone pulls aggro on a mob, I can look at that list and just whip the mouse wheel up or down to get right to that target, provoke or ranged attack, and all is good. I then have Alt + the mouse wheel bound to the party list, allowing me to do the same speedy zip-the-selection through the party list quickly as a healer. (My zoom in/out is rebound to Control + the mouse wheel.)

It takes some practice to land perfectly on your target in the list instead of one above or one below, but I made that binding change a year and a half ago and I have had a lot of practice with it now, and thus muscle memory of exactly how far I need to spin the mouse wheel to get to position 2, 3, etc. (Though it also probably means if I ever use a different MMO mouse with slightly different scroll wheel sensitivity, I'm screwed.) And while it was originally meant solely as an aid to finding that one mob in the list while tanking, it has proven to be an unplanned but considerable benefit in Crystalline Conflict due to the enemy team display being functionally a reskinned enemy aggro list; I can indeed flip from one target to another in mere instants, with nothing other than a standard USB MMO mouse.

Now, if you mean whipping between multiple targets and attacking them all in like, under a GCD, that's obviously cheating. But if you mean seeing that someone in the enemy list has a potentially-disastrous cast being prepared and it needs to be dealt with right now? And then immediately switching back to your original target before the GCD cooldown is even over? It is absolutely possible to select them almost instantaneously to deal with them just via the mouse wheel method (and switch back afterwards), once you've got the practice to land on the entry you intend to.

Like, I have the enemy in position 3 on the list targeted, but the one in position 5 needs to be addressed right now? I can scroll down <this> far and they're instantly selected, I do whatever I need, and then I can switch back to the original target even while the action is processing. (I can't do anything to the original target I switched back to until my GCD is off cooldown, obviously, but I can sure as heck have them selected and waiting again for that next GCD almost instantaneously.)

This is also useful with the party list, as you can select a party member needing a heal woven in; changing targets does not cancel a cast, so I can hit attack on a boss, select the target player while the castbar is still going, immediately weave the heal, and be back on the boss before the GCD is off cooldown. (No adds? Any movement of the scroll wheel without a modifier key re-targets the boss with this setup; there's only one entry in the aggro list, so no matter how many slots you move through, you only ever select the boss.)

Admittedly, I may regret sharing this trick now that it has proven so useful in CC, if I find more people using it against me... but it also doesn't seem entirely fair to keep a mechanical trick like that to myself when it really does make target management orders of magnitude easier, including in CC matches.