If that was all they wanted to do, they could have performed the checks they've patched in only when you try to use a car online. Cars in your garage could be marked especially (applied at runtime, not in the save) so that you and everyone else knows they're hybrids - the garage is automatically filtered anyway according to the room rules.
So, online rooms could have a "no hybrids" flag, set by default, so that those that want to use them and race against them can do so if they choose to. Of course, these checks easily extend to the seasonals, which is where the cheating problem was arguably at its greatest.
But no, they've got to do the angry Dad thing and break everyone's toys to remind us all who's the boss.
PD can continue to treat me like a criminal, but I know I've done nothing wrong, morally or legally. They could have embraced the wants of the community and cooperated with us to produce a system that prevents cheating in the places where it matters, and doesn't completely obliterate the reason so many people started playing the game again.
Instead, I'm being punished because they felt the need to stamp their supposed authority, (probably because Sony's PRs started screaming about brand image and piracy, the dullards.) In doing so they will have actively driven away customers, many of whom are not the sociopathic cheaters some opposed to hybrids seemingly like to assume they are. If anything, it's the sociopaths who will stay, because their particular kind of enjoyment (which, by definition, is at the expense of others) can still be expressed through many "legitimate" means in the game, so their fun isn't actually being stopped!
Perhaps PD / Sony should speak up about this, rather than pretend it's not happening.