What Walter said.
I have a pair of DaKines that is very close to his ideas, but of course they are no longer on the market.
The lobstrosity trigger-mitts work very well for cold handed folks.
Better than mittens. Modular idea should include these as well as mitts and gloves.
A pass window on the back of the hand might get ripped too easily while brushwhacking. A window on the cuff of a gauntlet would be better.
A squeegee would need to be very soft. Like SKI-GEE rubber. The ones I've seen are too hard and likely to scratch lenses.
Maybe a soft wiper on one glove for rain and a harder one for ice on the the other? Make them different colors - pink for rain, blue for ice. Squeegee on the back of the base of the thumb.
Snotrag patch on the back of the index fingers.
For the retainer cord, a little stash pocket to tuck them into if not used would be a nice touch.
The wrist cinch strap should be narrow enough to accomodate the width of a watch. Say 2cm (3/4 ").
For me, price is not as important as function.