Michael, last night I tried to do the coffee thing and it works great. I didn't have any triangle filters, but for the sake of the trial, I just used a regular 8-10 cup filter. I shaped it a bit in order to fit it to the capri sun pouch, placed a tbsp of grounds in it, then poured hot water over it. Just like a normal drip brew, it drained into the pouch. Good brew, good idea, good things.
Caveat: Be sure to fold down excess filter and hold on to it. The weight of the water had a tendency to draw the filter further into the pouch. By my conclusion, this all can easily be recreated on the trail.