My take on BIP-177 is that setting aside what display unit you want to use, this is just not belong as a BIP.

All the other BIPs deal with consensus or cryptography, I.E backend stuff you need to coordinate over. I.E silent payments, fork signalling, seed phrases and so on.

There are no BIPs for UI/UX standards, because you don't need to coordinate that. If you want to show the wallet balance in dollars, bits, sats or whole Bitcoin you can just go do it. There's no need to coordinate that. Hell, you can even make it a configurable setting in the wallet.

Also for that reason it's seems like tilting at windmills to try to define a "official" unit via BIP. We don't have a official UI/UX convention. I question the need to define such a thing, and if we did it wouldn't belong in BIPs anyway for the aforementioned reasons.