I’m against.
Melee attacks from zombies are already very weak, except at the very start of the game. Armoring self would become even easier than it is now, making zombies stop being a threat even faster than now.
Zombies spamming stun would severely affect starting characters, who would get wrecked by dogs and hunters, while not doing anything against armored characters.
There’s also the part where it could easily result in “bullshit” - getting stunned every other turn, getting stunned for so long you have no chance to recover, getting stunned by weak attacks and forced to stand in acid losing valuable items etc.
Finally it would nerf both lightly armored characters (who need to recover their dodges and move a lot) and heavy weapon users (who need all the time they can afford to swing) - both of which are already inferior to heavily armored characters and medium-speed weapon users, who wouldn’t suffer as much from the change.
As for player side - by early midgame, most player melee attacks are crits and thus stun. This is more annoying than useful, as it causes constant stumbling and makes zombies unpredictable. If crits were nerfed not to happen a lot, it would require reworking all those techniques that rely on crits to work.
The damage nerf would have to be something much more creative than just a flat nerf, or it would make weak weapons (sledge hammer, steel spear) weaker and barely affect strong weapons (nodachi, punch dagger).
Ranged stun sounds like it could be mildly useful for early game characters, but then the stun duration would have to be quite huge for it to matter. But I’d rather see it as a more active method of running away (something better than just kiting) than a combat initiator.
I see no reason for the grounding. It sounds like even bigger nerf for early characters, so that when they get hit, instead of seeing torso at 30% and 50 pain they get a gravestone. And the armor halving part would mean medium armors would no longer guarantee immunity from weak zombies (while increasing stun duration, as you said it’d scale with encumbrance), so once again heavier armors rule while light armors are a constant (but random and mostly player-independent) risk that semi-stunlock happens and ruins a character.
I don’t like player stuns because they take away control and put the character in the hands of RNG. Stunlock/confuse chain/stacked paralysis type deaths aren’t “fun”, they’re basically “you randomly died” types of death.
I’d much rather see changes like hulk smash ability. It was a simple addition that nerfed heavy characters (can’t be blocked, can be dodged, reduced damage on high dex), promoted mobility and made formerly weak zombie types a threat, while not making things significantly more bullshitty. Well, except for the part where it often damages the armor.