The following is a design for stack-switching that has a number of useful properties that seem to make it a good fit for the needs of this extension to WebAssembly. I have made an effort to address all the concerns that have been expressed throughout the lifetime of the Stacks subgroup to the best of my understanding of them. For example, I have checked that all prior proposals have a straightforward and efficient translation into this design, and I have identified a composability property that this design (but no prior proposal) satisfies. Please let me know your thoughts, and I am happy to provide a translation if anyone requests one.
When one performs a call $func, the currently executing function is conceptually left in a suspended state: it stores its current state (e.g. the values of its locals) as a frame on the stack and provides a code address to use to resume the function.