My sister has an aging Boxer, Sonny Liston, who she adores. He is exceedingly well-trained and her best pal. Sonny knows many commands and is her constant companion. But due to some medical issues, she is anticipating having to choose another dog soon and would like some "overlap", so as to integrate a new dog into the household.
Info: My sister is a single, petite, 40-ish lady who lives alone (don't get any ideas. She's heavily armed and doesn't suffer foolishness easily.) She is an avid hiker and camps out on the trail alone, with Sonny. She wants a dog that can stand to be alone while she works, but is eager to go out and play when she does. The new dog will be a house dog, but expected to be watchful and on guard, given her vulnerability as a single gal. But she really wants a dog with personality, too.
She is considering a Doberman, a Rottweiler, another Boxer, or a German Shepherd. She would like to avoid the genetic issues that would deprive her of her new pal prematurely, which is what is happening with Sonny.
And for those of you who don't have dog advice, but want to just get into my sister's pants, I am heavily armed, too.