Sorry if this has been asked before but I can not find it on the forum. Can the Mystic’s Meditative Focus be used more than once at a time? Meaning everything stacks for a +2 to a lot of things?
No, it cannot stack with itself!
Not that I don’t trust you but can I get a reason for that, a rule or even word of god that the designer didn’t intend for it to? I am not aware of a rule that says bonus types are limited. The line “As the mystic’s mind expands, so does his ability to maintain their focus” to my implies it could and the fluff of going into a deeper focus is not too out there.
Obi-Wan: Obi-Wan Kenobi. Obi-Wan… Now, that’s a name I’ve not heard in a long time. A long time.
Luke: I think my uncle knows him. He said he was dead.
Obi-Wan: Oh, he’s not dead… Not yet.
Luke: You know him?
Obi-Wan: But of course I know him. He’s me.
Ahh, thank you. The lack official emblem made me think you might be just a long time fan. Thank you once again.
No problem. 
And if you want Mystics to be able to stack their meditative focus in your campaign, go for it. Every campaign is a law unto itself, etc.
to add my own two cents: you’re unlikely to break the game by permitting this, as being high level enough to do this often means facing threats for which it would not be overpowering. Instead, you are merely adding additional incentive for the “15 minute workday” where the party feels the urge to blow all their resources and “go nova” only to rest and regain all the spent resources to do it again. This already exists due to wizards and other spellcasters, and ACKs thankfully has some rules for dungeon crawling that help deter this behavior, but in the wilderness there’s likely only going to be one encounter per day, so those will all be fights that involve going nova, and the overall lethality of wilderness will therefore become somewhat muted in parties with a mystic. But the wilderness is really deadly, so I wouldn’t worry too much!