Probably been suggested before but: Use bits not satoshis. sats are too small. Long term, bits will be like dollars, sats like cents. Standard should be to denominate everything in bits.
Just as I pay three dollars for coffee, not 300 cents, I would prefer to tip five and a half bits rather than 546 satoshis...
The problem is that you will have to pay like 5 satoshi for the coffee once Bitcoin is widely established, because of the drastic value increase that comes with.
If that actually happens we would have to change the protocol to add more digits, for divisibility... Then the whole paradigm would have to be changed anyway.