I have a number of packs to choose from. If I'm pretty sure I'm going to harvest a critter my preference would be something similar to CoHiCountry using my Kifaru frame with Timberline bag that compresses super small and has lots of pockets and is capable of packing out 100+ lb loads if I get something. If I'm planning on covering lots of country I'll likely grab my old reliable Badlands 2200 that is lighter weight than my Kifaru setup has enough room for the bulkiest items I may carry on day hunts such as my spotter/tripod, plus raingear/coat, etc if needed. If I'm spike camping I'll convert over to the same Kifaru frame plus EMR2 which is capable of loading as much gear bulk and weight as I can handle. I'm going to sell my Sitka Bivy 4500 because I like the Kifaru setup so much better. It's really nice having a selection of packs to choose from because it's pretty tough to have 1 that works well for several different jobs.
With that said, if I wanted 1 super light daypack I'd likely make sure it is large enough for raingear, coat, spotting scope, tripod and my bulkiest gear. I always like additional straps so if I happen to get a deer or elk I can pack out a decent amount of meat, cape, antlers, etc on the first load. Extra straps are also nice for hauling out antler sheds (which I do a lot). I would also pick a daypack that doesn't have noisy zippers, velcro, fabric, and has quick and easy access to the gear I use a lot. Another feature I would look for is straps or some way of securing rifle, shotgun, or bow to the daypack so both hands are free. Lastly, all of the packs I own are waterproof! There is nothing worse than having wet gear!