Microsoft Research had an experimental OS project at one point that does just that with everything running in ring 0 in the same address space:

https://en.wikipedia.org/wiki/Singularity_(operating_system)

Managed code, the properties of their C# derived programming language, static analysis and verification were used rather than hardware exception handling.

Fil-C vs CHERI vs SeL4 vs YOLO

I think hardware protection is usually easier to sell but it isn't when it is slower or more expensive than the alternative.