Seems that a Pixel 5 without 5G would be a seriously missed marketing opportunity. The so-called "millimeter wave" band will never be more than a gimmick, because of hard limits on propagation and the prohibitive cost of running high speed fiber backhaul to support more than a few scattered hotspots. So forget about the high band, or make a vendor-specific model that they can sell locked. I'd rather buy an unlocked phone straight from Google that has excellent low and mid-band 5G capability, no high band at all and a price tag under $1000. A name like "Pixel 5G" seems corny to me, so I'm sure that AT&T or Verizon would love to sell that to their customers.
As much as I'd like removable storage (and battery), I'd be willing to do without if the phone was waterproof (and if the non-removable battery was significantly larger on the XL). I already own still and video cameras with optics that will always beat out a skinny cellphone, so I don't need anything more than an adequate camera. I got a pocket camera with a pop-out zoom lens, and while it's a neat feature for a pocket camera, I wouldn't want that sort of fragility in my phone. Put in a dozen fixed focal length lenses if it makes people happy, just don't make the device too fragile to take places.
A fingerprint reader right where I now expect it would be ideal. Facial recognition (like putting my DNA on file when I'm not a criminal) is too "Nineteen Eighty-Four" for me.
A back made from anything but glass would be a nice change. I liked the choice of backs on the Droid Turbo 2, if Google offered something similar, I'd like that. If Google offered trick snap-in (or magnetic) backs that did double duty as a protective case, and allowed access to micro SD card & removable battery, I'd be over the moon!