Nice proposal!

However, I think the mess will stay for as long as there are two different tagging schemes. Therefore I suggest to abandon either highway=bus_stop and railway=tram_stop/halt/station or public_transport=platform.

My preferred solution would be to:

• Abandon public_transport=platform and continue to use highway=bus_stop and railway=tram_stop/halt/station, because it’s clearer what these tags mean and they are easier to map
• Map railway=tram_stop beside the road, where passengers wait for the tram
• Only add highway=bus_stop and railway=tram_stop/halt/station to route relations
• Map actual platforms with highway=platform or railway=platform (same as your proposal)