And it's in your interest for workerd to never include all such things..
My best guess is that you are suggesting that we should open source our multi-tenant hosting technology, along with workerd.
But this doesn't make sense. No popular JavaScript runtime includes multi-tenant hosting technology. Multi-tenant hosting is the responsibility of the hosting provider. workerd is compatible with other providers' multi-tenant hosting approaches. You do not need our specific technology in order to run Workers apps on other hosting providers, and in fact would not even be particularly useful for that purpose.
(But I admittedly have not actually asked Ryan if he had long-term plans to add a multi-tenant scheduler so maybe I'm wrong.)