As the name of the title, I have made a plugin called Switchr. Switchr is one simple command (/switchr <player 1> <player 2>) for people who have the built-in permission (swapr.allow) and it can:
Before you ask about a config.yml for this, I will not add configuration because it simply doesn't need it. If you see a good reason for it, then you may comment that idea.
This is all balanced because if you look at a switched player, it shows their real name and skin. Hopefully I can get potion effects and inventories, but I am a beginner to Minecraft plugins and to Java.