Smaller dog

My family has had our dog since he was a puppy (now 6). He has always been a backyard dog, as he is half Lab and half Rot Weiler and is huge. We rarely let him go inside the house because he sheds a lot. I am thinking about getting a smaller dog just for me that I would keep indoors, but I’m not sure how my older dog would react. I mean I know he will get jealous, but I’m not sure how bad it will be or if it would start to affect his health in any way. Any thoughts?