This isn’t possible today, but you’re definitely not the first to ask about something similar! This feature request keeps coming back, and I’m starting to see it could be some way for gradual adoption.
I’ve been thinking about “Hologram Widgets” that you could inject into existing SPAs or LiveView apps, or use auto-transpiled code fragments like in your case. Your validation logic scenario is exactly what this would be great for.
No timeline yet, but it’s definitely on my radar.
