One rifle to do it all is easy! A .308 Win bolt action with a 3-9X40 scope. I'm not going to go into the brand of either rifle or scope. I know I'm going to get grief for this next comment but modern rifles are Ford Dodge or Chevy. A pick up is basically a pick up and each has it's following. So with that said I will defend my bolt action rifle with the fact that they are accurate, easy to fire and reload, and come in many configurations to please the shooter. A bolt rifle can be had in Stainless, Varmint, wood, lightweight, and even full stocks. There can be a quick follow up shot if needed with a simple flick of the wrist.
I will defend the .308 win with the simple word of variety. There are a whole slew of loads for this little round that will meet the need of any shooter, young or old as well as handle all eastern big game be it White tail, black bear, or Moose. From the 125 grain reduced recoil loads to the brush bucking 180 grain round nose soft point. I know the round does not beat the brush but it does have a large frontal area that allows for larger deformation and energy transfer but still has the power for deep penetration. I think the two factors of soft round nose and quick energy transfer are reasons why some rounds built a reputation for brush bucking and anchor the deer where you shot it, while other cartridges with more power did not, due more to bullet design.
Personally my eastern deer rifle is a Ruger M77 or Dad's Sako Deluxe, neither wear a scope but my shots are not far ( Usually well under 200 yards) in either eastern North Carolina or in upstate New York where I started deer hunting. A 3-9 scope will allow for those who do not shoot as much as I do to be on target easier and quicker not to mention give them the confidence factor of the cross hairs.
McWoodduck