Love the effort the Angular team is putting into these RFCs, I have been very impressed as of late! (not that I wasn't impressed before that is!).
I agree that the latency really stymies the effectiveness and creativity of developers, especially when making "small" changes (this is a relative term based on your specific scenario obviously). HMR _can_ be a way around this but I have yet to see an implementation that works really well. I have always wanted Angular to embrace a more parallelizable compiler (although the compiler up till now has been fantastic), as large apps start to get a little iffy (other solutions to this obviously, such as incremental compilation from Nx, micro-frontends using module federation etc, but these are all more involved than optimizing the compiler, for the dev obviously, not for the angular term persay). I actually wrote a blog post on the bundle size/speed for our companies code base ([URL] as I have been interested in this for a while.
I like the idea of being able to allow for type checking to be more of a lint check but would either need to be well thought out since as [USER] mentioned type checking gets more important the larger the codebase or it would need to be opt in.
We use Nest and Nx at Trellis and the way `nx serve <nest app>` works is it will actually restart the server even if there are type errors and not hold up the refresh cycle. This can be handy, except when it's not, ie. you didn't notice you forgot to pass in a new function parameter and thats why your endpoint doesn't work, for example.
In my opinion **extreme** is the long term solution here, other tools are starting to integrate and support non TS based tooling (like esbuild and swc) as they are written in Rust or other more performant languages. I love Angular and don't want it to fall behind in terms of compilation performance or DX because it is not embracing new tools. Of course I realize this is a major lift and will take a lot of time and effort so I don't expect the Angular team to just go and implement it overnight but do strongly believe we need to keep up to date with tooling. The Angular CLI has always been one of the best selling points of Angular and one of the best built in CLI tools out there, let's not let it fall behind.
All in all, I love this RFC and support optimizing the pipeline wholeheartedly, the better we make it for the developers using it the more people will use it and love it.