A lot of the responses make sense, but also show how individual situations vary.
A few thoughts:
As to flat protection, instead of using heavy Schwalbe Marathon Plus-Style tires, I've been considering just going tubeless and using road bike tires. Have commuted on tubed Conti 4seasons for a while and had zero punctures from penetrations over a year (just snakebites). So, switching to something like tubeless Schwalbe One tires should be reliable, but add a bit of comfort and thus speed.
A base assumption of mine for this thread is that secure indoor storage is a given (it's likely).
Over time, I have moved into the group of people who wax their chains and/or use wax-based lubes (squirt). The purpose was more to keep them clean during winter use (to not stay a lube thread: this works well for me, but I recognize that others will have differing experiences and circumstances). A nice side effect for me has been that cleaning the bike is so much less needed now. So my plan would be to just keep 2-3 chains in a wax bath rotation (or use squirt). That would not be as trouble-free as a pinion, but close to it with much less weight, cost and efficiency losses.
Lastly, I assume that (as others have pointed out), weight/aero gains will be meaningless if I have lots of cargo to haul each time. So, a little bit of storage of essentials at work and the occasional car (share) trip to replace 1-2 weeks worth of items should allow to cut down on items.
I'm not going to make this a race. But even when not cycling at 160bpm all the time, it is nice to go relatively quick. And fun, of course
Winter is a different beast, which will need its own solution (and if it's bike based, I probably already have it in my stable)
Edit: or I just upgrade my recumbent with an e-assist....
Edit2: about the route. Imagine it's your 50km Sunday ride, just each day. It's one of my favorite recreational routes, so none of the usual commuting city grind and traffic issues.