Would such a thing be possible in Android world? I wonder since there are so many phone manufacturer and ISP mods that might not be under Google's control.
Every third party browser you install on Android already has a differeny JIT, so all those apps probably need to implement their own rules.
GrapheneOS[1] includes similar 'defense in depth' mechanisms of which predate and some go above iOS 'Lockdown Mode'. Unfortunately just for Pixel devices.
Android fully supports alternate browsers (you don't have the "skins" for the Apple engine that you get on iOS) so nothing is stopping e.g. Firefox from introducing such a mode.
But that's only a single application. Lockdown Mode affects the operation of the entire OS, and all applications that use certain iOS features.