Is it possible to disable CPU throttling on a MacBook Pro with a completely dead (not recognized) battery?
Not practically. You're better off selling the computer for parts or getting a replacement battery / having the Mac serviced by a professional. 

Non user replaceable batteries are very vulnerable to damage and lithium battery fires are no joke. Even global companies have struggled with making safe products from brand new parts (galaxy 7) so please don't cut corners on safety when Apple batteries are involved - especially with repair parts or unauthorized / uninsured repair shops.