Is there a way that the fricking in game can be compatible with a "Plug"/other toys?

There are no such toys at the moment, but maybe they will be added someday. You can join the discord and write your idea in a special channel.

Only Sex Toy that is compatible with this game is A-GUI Masturbation Cup. There is still no other Sex Toy beside this one that is specifically made to be compatible. If you wanna use other Sex Toy, you have to figure it out yourself.