There is no written rule about how old regiments have to be, you just pulled it out of your magic hat aka "I fuck you at every tournament by being arbitrary", If a rule is not written, it's not written, you can't create rules like that suddenly and even if you want to add one you have to at least make an exception for us who put our sign up before the rule was added that's how it works in law.
Anyway, it doesn't change anything 2eFusGre or any other name we're gonna play together no matter what, you prefer that we all go in an EU regiment to be even more stacked or that we take our french regiment that exists for 3 years ?