For the temporal thing, that's absolutely fair and completely understand the worry but since most workflows are about the steps and not the glue between them, you will be able to reuse most of your code. However, temporal is quite an heavy format for writing workflows so of course it will still be a bit of work.
Our views support our retool like builder but also full react apps, or svelte, or vue, or anything that can compile to an iife. The example provided above can be iterated on with just a simple 'npm run dev': https://github.com/windmill-labs/windmill-react-template