Sorry Oliver but you are wrong on a few things here.
'Motor-free', 'car-free', 'fume-free' etc. all work better.
They don't. We've worked with these before and they carry a certain amount of baggage with them around who uses them and some of the perceptions of what they're taken to imply. In an environment with a broad range of politics, culture and backgrounds they can be toxic to your endeavours and lead to a contagious dismissive attitude. We could very easily grind our plans and proposals to a halt. We knew the risks around use of the term "pedestrianise" and the alternatives available and we had some frank internal discussions about what to use. Sometimes knowing your audience is more important than idealised terminology.
The associated imagery has been useful too so when we've started to talking to people about this, they've already come to the assumption that bicycle will be included too. You say "they will inevitably not think of shared use and cyclists" but "they" are already proving you wrong. You might want to be careful of that sort of use of "they", it can be quite divisive and tribalistic. You say "it squeezes cyclists out" but despite the risk, we're already working past that.
Fortunately language isn't the only issue. There's been some important underpinning work around this being a thing that will include cyclists. If we get the management of it right the first time round, that will be a foundation piece.
This is always a problematic, negative idea
You might think that but again, we're back to knowing our audience and the strong value of calling things what they are. I could say all the stuff you have about modal filters and car-freeness and what I'd get back is withering looks and a telling that I'm closing the road. To some people a road closure is the clear and literal you're looking for. Knowing your audience is almost definitely more important than tickboxing your terminology.
If retailers are going to be objecting the loudest then we're pretty much home free for a permanent change because they have genuinely been our biggest supporters. Sadly they aren't the loudest objectors so we'll probably have a bit more work to do, not all of it with them though.
And yes, the deliveries (some) and access to private parking (none on the street we're car freeing) were all scoped out and planned for very early on in the process. As was early discussion with members of the emergency services and making links with the local pan-disability access liaison group.
Be careful of planning for setbacks and delays. I did and then the Council did a lot of heavy lifting to make things happen quickly. If I'd known that, I would have done things differently.