[Ner0]

I'm coming from 5th so going backwards is confusing me a bit. I get how Weapon Foci work. Attune to it, get bonus dice equal to it's rating and the ability to smack around spirits and stuff who aren't normally effected by mundane means. Where I'm confused are power foci. I recall in 5 being able to get some cool power-tattoo foci that gave me equivalent to adept powers. That around in 4e? What's the point to Adepts and Foci besides Weapon foci?

[SpellBinder]

Qi foci don't exist in SR4, but they certainly can be rolled back into that edition.  Probably up the karma cost to 3 x Force to keep in line with the rest of the foci of the edition, but the rest of the SR5 rules for qi foci can be used straight across.  Beyond that, as there's very little that an Adept can benefit from a power focus as so few of their abilities  actually draw on their Magic attribute directly.