Yea, That's part of the reason I'm getting a 2nd dog after about a year. As far as exercise, once trained to the radio fence they will have total freedom of the 3 acres. I do plan on letting them in the house (limited areas) on a daily basis for family time but once it's time to go to bed they will go outdoors. One thing I like about the radio fence I'm looking at is that they have small modules you can place in your house with an adjustable range of 2ft to 10 ft. It integrates with the base. That way I can limit them to specific areas of the house.
I've seen dogs trained not to cross a threshold into the kitchen before without a radio fence but I like the idea of having the same type of deterrent on the inside as I have on the outside so I plan on keeping them out of the carpeted living room area.
Definitely not going to have a dog of that stature inside full time due to the what has already been mentioned.