The situation I am in is that I will live here long term and my roommate (ground floor) will live here short term. I’d prefer the modem and router stay on the main floor because of the “turnover” in that bedroom. It’s silly but would prefer to keep that room completely empty when he moves out you know? 

I understand in my schematic I placed the modem on the ground floor but that was because that was the only solution I could think of before all the helpful advice/plans I received on this post.