I agree with your reasoning, but the thing is, you are forcibly making an issue somewhere where there is not one. OSM already has a clear distinction between ways which can be used by peds, by cyclists, and by other transport methods. Your tagging does not actually fix anything (there is no issue) and just makes the maps harder to work on. Following your approach, you would have to update every single footway in the world which is clearly a waste of time. Instead of "fixing" non-issues how about we spend this time on something actually more productive. The issue you are thinking about has been already resolved by default access permissions, whether you are aware of it or not.