<p>I think the main things we'd be looking for would be:<br>
- a clear explanation of why a new metaclass is considered too complex a solution <br>
- what the implications are for classes that have nothing to do with the SciPy/NumPy ecosystem<br>
- how subclassing would behave (both at the class and metaclass level)</p>
<p>Yes, defining a new metaclass for fast signature exchange has its challenges - but it means that *our* concerns about maintaining consistent behaviour in the default object model and avoiding adverse effects on code that doesn't need the new behaviour are addressed automatically. </p>
<p>Also, I'd consider a functioning reference implementation using a custom metaclass a requirement before we considered modifying type anyway, so I think that's the best thing to pursue next rather than a PEP. It also has the virtue of letting you choose which Python versions to target and iterating at a faster rate than CPython.</p>
<p>Cheers,<br>
Nick.<br>
--<br>
Sent from my phone, thus the relative brevity :) </p>