Gung-Ho says one player may use a power now. It doesn't say you can only use powers in your area.
Prejudice is spceifically by Pride, and so you can use it even if it is in another play area. Similarly Ammo cards say "play next to a gun card" That gun card doesn't have to be in your play area.
The hard part is trying to figure out which category the symobl effects will fall into.
This isn't isolated to this promo though, all Guise has to do is use "Uh yeah" to gain a form card's "you may activate" text.
If it works then this relationship is broken, because Guise would be able to abuse Bestial Shift at the same time that Naturalist is. Example that we actually did before deciding not to let it work like this at all.
Guise has Uh Yeah copying Naturalist, Naturalist has Gazelle in play.
Naturalist plays bestial shift. Guise goes first, naturalist regains 3, Guise uses Gazelle's power to also regain 3. Naturalist then regains 3 and uses his innate power to pull out Crocodile.
Guise now actiates BS's Croc text, naturalist deals something 4 damage, Guise uses Tough choices, playing Best card ever and Look what I found to deal a total of 10 damage (croc boosting) then Naturalist goes, dealing something 4 damage and using Croc's power to deal 3 damage.
Naturalist regained 6hp, Guise regained 4, Naturalist dealt 11 damage and Guise dealt 10, 4 of which were directly because of this combo (the rest from his 2 cards played).
I expect the answer to be that it doesn't apply to effects in other play areas, because that is the most balanced, but the Video Game rulings aren't all falling in line with balance so who knows?