Honestly, I think letting people include their own code is good, people will always want to do things that you couldn't have imagined yet, and for their own good reasons.
However, you need to make sure the platform can eventually catch up with the de-facto standards people are coming up with, so that people don't keep having to keep on re-inventing these wheels. As a comparison, see how JavaScript features evolved from jQuery and Underscore features.
> But I think the mindset is to stop thinking the website for just the browser.
I agree. I'd suggest that you think through how you can convince people to stop thinking about the website as just for the browser.
In the last decade, many people might have thought that the rise of the mobile web would made web developers separate presentation from content. But instead of using the same HTML with different stylesheets, what actually happened is every major website started maintaining two completely separate websites, one for web and one for mobile! I'd recommend thinking about why this happened, to make sure your framework doesn't nudge people down the same route.
However, you need to make sure the platform can eventually catch up with the de-facto standards people are coming up with, so that people don't keep having to keep on re-inventing these wheels. As a comparison, see how JavaScript features evolved from jQuery and Underscore features.
> But I think the mindset is to stop thinking the website for just the browser.
I agree. I'd suggest that you think through how you can convince people to stop thinking about the website as just for the browser.
In the last decade, many people might have thought that the rise of the mobile web would made web developers separate presentation from content. But instead of using the same HTML with different stylesheets, what actually happened is every major website started maintaining two completely separate websites, one for web and one for mobile! I'd recommend thinking about why this happened, to make sure your framework doesn't nudge people down the same route.
Again, wishing you success!