If you're going to run Python code inside a WebAssembly container anyway why go with the Monty subset when you could use full CPython (or MicroPython) compiled to WASM instead?
2. Suspension and resumption. Monty's VM state is fully serializable so I can run the VM until it gets to a tool call and persist the VM state. I could resume it days later with the results of the tool call with no issues. Doing that guaranteed with CPython is really tricky (tools like Pickle can get you close but if you have open sockets or other weird stuff you're in a world of hurt).
Your point 2 is very convincing: I hadn't realized Monty had serializable state as a core feature, that's a very compelling attribute for an agent runtime! I have my own projects that could benefit from that.
Serializable state is the most cool property though. It's really undersold in the explanations but makes running durable agent workflows authored in code possible!