this actually seems like an reasonable technical solution to the non-technical problem that causes deprecations to be ignored in the first place

Degrading performance exponentially (1ms, 2ms, 4ms, 8ms...) WILL create a 'business need', without directly breaking critical functions. Without this degradation, there is no reason to remove the deprecated code, from a business perspective.

It should slow down your compile instead of the runtime. That way the pain is felt by the developer who can fix it.