As a fellow Rocky Mountain fly-fishman, I feel your pain about taking all of the additional gear needed, and of course the endless mosquito attacks.

Some suggestions:
- I long ago stopped bring wading sandals. Most of the streams I have come across in the backcountry are rather narrow and no real advantage is gained, most of the time, by being able enter the water. In fact, more often that not I find myself casting further-back or in a low-profile position as to not spook the fish. Lakes are the same, I just fish from the bank-- I perhaps lose 5-10ft of distance in most cases.

-Ground cloth, go to Home Depot and grab painter's drop cloth or window covering. It's cheap and light.

-Water in the Rockies is plentyful. I just take one 2L Platypus and one Aquafiner water bottle. Walking the minium 100yrds to a water source is a minimal inconvience that I do once a day.

-Cooking fish. Nix the grill toppers and just wrap your fish in tin-foil and place directly into the coals of a fire. How do you cook them if fires are not permitted?

-I would probably nix the poncho-tarp. You have a rain jacket, rain pants and your tent.

-Your DEET problem is easy. Purchase liquid DEET and repackage into small dropper bottles. No need to then bring the big spray cans.

-I think most people get by with just a headlamp. I can't think of a need for three light sources.