Similar to most of these comments I think this is a very interesting take and agree with a lot of it! I want to make a few points, mostly because I just love talking about these components 😎.

- As mentioned in comment, checkboxes and radios can still have same size targets, but their perceived target will always be smaller as you'll never have confidence that the text / padding is clickable without a border. So agree with your sentiment there.

- The whole argument of the "dot and checkmark cue" being confusing I don't think holds that much weight as I think it is pretty universal. Furthermore, you end up using the checkmark part in your multi-select so it's not like it's been abandoned.

- Iterating off your great ideas I would further distinguish your single-select from you multi-select by still adding the radio circle in the single-select chip and then for multi-select I'd make the check circle less round (maybe even the whole chip less round). Some of the selected states for the single-select you show will be difficult to keep accessible AND have a clear focus state.

With what I'm proposing this we get the improved layout, the larger perceived targets and a clearer idea of if a chip is single or multi BEFORE it is selected.