Maybe if Freedom of Movement didn't *completely negate* an entire combat style it wouldn't be important to ignore it?
Who said Grapple was a "combat style"? It's an optional attack, one of four special types excluding what attacks are supposed to do, that all creatures in the game can use and PCs have the biggest disadvantage in this area compared to larger creatures that have a huge advantage. Immunity to Grapple is a balancing mechanic designed to increase the survivability of PCs.
Casters already too strong, and they can just ignore entire builds with single spells
Actually, most of everyone's top protection Spells such Protection From Evil, Death Ward, Mindblank, Anti-Magic Field, Dispel, and yes Freedom of Movement because Grapple is just one tiny aspect of it, and so on are all anti-caster things that a mundane typically doesn't even care if his target has.
But they in every single way make that mundane more effective at dealing with caster than if he couldn't use any of those and that is utterly inarguable. Banning them actually makes casters even more powerful than you already perceive them to be.
I guess it's Q&A time.
Q: What's the save against whifing your grapple attempts on Mirror Images?
A: Blindsense, totally negates Mirror Image since the figments relay on sight, and your Mechs can all have it.
Also Scent which is available as a 1st level Tiger Claw Stance and trained dogs.
Q: What's the save of automatically failing your grapple against Heart of Water at 5th level?
A: Seeing how you've literally chosen to ice sake up hill to prove how badass you can optimize, try optimizing some more.
Also your Attack Action just made them burn a 4th level Spell which is a pretty fair trade seeing how you probably get more than four of those per day, or in a single Full-Attack. And if you were seriously about Grapple you'd probably have an Improved Grab like ability. So the the attempted Grapple is actually just an added bonus after dealing your full damage and trying to kill them anyway.Q: What's the save against trying to reach the mage's that flying above you?
A1: Remind Ols to stop hating ranged weapons before he forgets they exist.
A2: Try flying after them using a flying mount that costs less than 200gp and lasts longer than five minutes.
Q: What's the save against abrupt jaunt?
A: If you're using a Ranged Weapon, just continue to shoot them in the face anyway. It's almost like ranged weapons are a very important and integral part of balancing the game or something. If you're melee, seeing how this is a very specific Class Feature that one and only one Class gets in the entire game I'll just throw out a Feat to counter it, Martial Study[sudden leap]. Also, than range on that is only 10ft right? Reach+5ft step or the 10ft step Training dummy work too.
Q: What's the save against the caster just using magic to turn themselves even bigger with a massive Str boost?
A: Giggle manically at how stupid the player is. Then, if he wasted an action on it, stab him in the face. If he Persisted, then it's probably a high powered game where you can buy your own Str Boosts and stab him in the face anyway. Otherwise, apply liberal usage a Ring of Freedom of Movement which is one of the contributing factors to why Spellcasters should not use Polymorph to turn into brutes and try to pretend they are a Martial Adept.
I'm not necessarily saying D&D is balanced. However this thread has taught me that you are extremely short sighted. You don't even pay attention to over half of the rules because they don't thematically appeal to you, you don't view the rules as a whole, you can't see how things connect, you don't even try to follow the chain reaction that happens each time you alter a rule, and perhaps the greatest thing of all; you do not create a plan or even envision the end goal before approaching a subject. Like if you wanted creatures to bypass a mundane's anti-supernatural gear to reinforce caster supremacy, why didn't you at least try to remain consistent? Every other immune-bypasser respects immunity and nerfs it into a bonus so why doesn't FoM in your homebrew just negate Size benefits as it's type of bonus?