priority zero definitely removes it from the status list without removing the effects, but it doesn't "auto set" the effect in place. Is there a script for force activating a specific skill?
There's an easier way to achieve this.
Firstly, make your status effect with priority zero and then your skill with a 'scope of 'none' and an 'occasion' of 'never'.
Secondly, go to your Database and insert a new 'Common Event'. After that, add a new conditional branch.
The settings for it should be as follows:
Obviously replacing the actor with yours and the skill you want.
Now, we need to set a switch for when the player acquires the skill. For mine, I used an NPC event who gives the player the passive skill, thus activating his switch and then in turn activating the common event.
Now return to your common event and set the 'Trigger' to Parallel and set the 'Condition' switch to the one you just made on the NPC event. And for an event action under your conditional branch make it as shown below.
Assuming you've made your status effect change the stats (I made mine boost his P.Def up 100%) you should be able to go and talk to the NPC event and acquire the passive skill and see the changes.
I've included a demo at the bottom of this post for reference.