It would either be a normal episode but with two of each character and one of them is opposite to the other.
Or if Himayura goes by the fanthingy, the 2p's will be murderous psychopaths, in which case the episode will probably scar all hetalians for life.

If there ever is going to be an episode, I do hope the 2Ps aren't evil. I don't like it how the fans say that they're the 'evil' side. -.-

I'm sure I'd be alright with it. As long as it's not the 2P's fans made which, I'm pretty sure it is highly unlikely that if there was a 2P!Hetalia episode they'd all be psychotic murderers. 2P!Hetalia is, if I recall correctly, just recoloring and different uniforms. The fans just made them evil. I think it's more likely that if there was a 2P!Htealia episode it would be the official designs not the fandom designs. Hetalia becoming evil and psychotic like 2P!Hetalia even for one episode sounds extremely unfitting. It's about History not senseless killing and murder. If it's the official 2P!Hetalia and not the fandom one, then I think I'd be okay with it.