Why should a fighter have to equip a sub-optimal weapon like a staff, just to make a trip attack?
No one is arguing this. Pretty much everyone agrees that Shove Prone should be an option available to everyone instead of Shoving Away, per 5e rules.
But dealing damage + tripping? That's different and it makes more sense to restrict that to weapons most suited for it: quarterstaffs, spears, etc..
What if you are already attacking with Disadvantage because of Bane or Blindness or something? Special attacks should be turned off that point or they would be essentially free.
Anyway, Larian isn't going to implement something that will make players miss more often since they are already struggling with it. The effects could be strong enough to still be situationally and tactically worth it, so hopefully they would at least consider something. Pin Down is already so weak it's effect is almost undetectable. If you succeed in something that can only be used once, or comes with a penalty, it should actually do something when it lands.
They could make it like GWM and cause a -5 instead of disadvantage. Though I prefer your idea of turning them off at that point.
But true, it is unlikely that Larian will implement additional sources of disadvantage for basic-like attacks. I agree that Pin Down should be stronger for being a once-per-short-rest ability, as should Bash.
