Absolutely not. Run them simultaneously, disconnected as much as WOW Classic is from Retail, sure. But WOW Classic should always be available as WOW Classic for those who want it.
I very much want TBC Classic, but I want it to be a choice. When I log into my account that I’m going to have to pay for, I want to be able to choose between WOW Classic and TBC Classic - two games for the price of one. Retail doesn’t count because I won’t touch it.