Personally, I'd go with a 7mm Rem Mag or 300 Win Mag as ONE all-around cartridge... I have quite a few guns, so I don't have to worry about this lol. I usually shoot my 22-250 Rem or 308 Win for practice/chuck hunting, my 7mm Rem Mag or one of my 308 Wins for deer hunting, and I'm looking into having 338 Edge built
. But my Ruger 10/22, 17 HMR or my 222 Rem are my squirrel hunting/plinking guns... All right, I'll stop before I write a thesis paper...
What about switch barrels, have you thought about that? Get 2 bolts, one in a magnum face and one in a standard face. Get one barrel in 308 Win and another in 300 Win Mag (on a long action of course). Almost any action can be converted to a switch barrel, but perhaps Savage is the easiest.
Not trying to muddy up the water lol, but it honestly sounds like you may need more than one caliber for the amount of shooting I believe you want to do. 30 cal has the widest and probably "best" selection of bullets to choose from. 7mm has a decent selection also.
Good luck, I wish I had your dilema