Don't know if you're even allowed to load on Princes Street, thought they had to go in the back via Rose Street and its lanes which is 8pm to 10.30am iirc.
I've been mulling this over trying to think of ways we might try lobbying for things to be tweaked on the assumption that, unless the plans here are just being put forward as they are so that the council can let Spokes object to it and blame limiting loading and taxis on them, they're intent on allowing a pretty significant amount of motor traffic on this "cycle street". How about this: narrow the roadway from 6m to 5m, 10mph speed limit, explicitly forbid overtaking of cyclists by motor vehicles, and finally limit motor vehicle access to two one-way routes - ie you can move east-west from St Andrew's Square to Frederick Street, and west-east from Charlotte Square to Frederick Street, then you *must* turn down Frederick Street onto Queen Street.
It's still yet another compromise we shouldn't be expected to make on what is ostensibly a main strategic cycle route, but it would at least make the street less useful to taxis and trucks as a ratrun to avoid Princes Street & Queen Street during rush hour, which is all it will be under the current plans.