The data model there is fundamentally different. That would break how git would work because operations that worked one way before would now no longer work that way. You'd functionally have rewritten and mapped all the old functionality to new functionality with subtle differences, but at that point is it even git? You have a wrapper with similar but subtly different commands and that's it. It's like saying "instead of reinventing functionality by building both ext4 and btrfs, why don't we just improve ext4"?

The two are practically entirely different.