The in between

This is a dimension that's in between the nether and over world. To access it the player would need to be inside a nether portal, while they're being warped to the nether they'd need to light some TNT so that it blows up the portal just before the player is warped into the nether. If done correctly the player will be warped into the in between. This dimension is a combination of the over world and nether, by that I mean some chunks may be over world parts, others maybe nether, and some may be a combination of both. Anything the player does in the in between will either appear in the nether or over world depending on what type of chunk they built in. In order to exit the in between the player would need to either die, sleep in an over world chunk(the bed would explode), sleep in a nether chunk(bed doesn't explode), or get a nether star. No the player wouldn't need to fight the wither because 1 any mobs in the in between are in their own world and can't see the player, and 2 the player is technically a ghost in the in between so they can't deal any damage. In order to get a nether star the player needs to find a ruined portal and activate it, causing it to explode and drop a nether star. After entering the in between the in between would be easier to access. I don't know how so it's up to Mojang or the comments