I'm probably not going to be the one to figure them out, but like I suggested, hot reload on every keystroke is the first thing that comes to mind. It's probably better not to think of Tailwind CSS on its own here, but rather as one super fast part of a broader super fast build pipeline. Making Tailwind fast just means it's not the blocker. Imagine combining 10 or 20 tools that all have sub-millisecond incremental build times.

LLM trying design using tailwind, stuff like: try to recreate this bitmap image using tailwind utility classes; the iteration speed for that kind of tasks depend on such speed.

Live reloading