I came up with this off the top of my head. This was inspired by the Light/Dark areana
Name:Portal Nexus
This areana is the middle ground from where every realm is interconnected. The areana is a pretty detailed site. It's floor is red stone and sand, there are giant pieces of land floating in the backgrounds and a constant lightning storm serves as this areana's hazard. The areana has a red sky with a vortex in the middle of it, kind of like a black hole or the Dead Zone for you DBZ fans. There are subtle reminders of different stages that have appeared in the MK games. For example, in one part of the areana there would be a broken version of the Warrior Shrine from MK1. In another part, there would be the Armory from MKII. It would have the molten steal and some broken pillars, but obviously there would be no walls behind it. Another stage would be Kahn's areana from MKII. His throne is destroyed, along with half the stands in ruins. This is one of the few solid barriers in the areanas. The swirling vortex would have some cool functions. For one thing, this vortex can bend time so as the players fight it out, you'll be able to see random matches in the background taking place from previous MK titles. So you can be playing as Sub-Zero against Scorpion and you'd see a match from MKII with Sub-Zero vs Scorpion in the armory. These "flash backs" would appear as spectral images in the background. The vortex can bend space as well. So as the fight moves on, you'll be transported to a different stage. You may start out in the Nexus, but might end up in the Slaughterhouse 20 seconds later. This kind of dynamic will drastically change the way people will play the game as it always shifts the enviroment around the players causing them adapt to different surroundings. Each time the characters are warped to a different stage, there will be a 20 second time limit before it shifts again.

Here's one of the cooler parts. Suppose you're warped to the Spider Temple stage, and you manage to get the Thoraxe stage weapon, if you still posses it when the stage shifts to say, the Netherbelly stage you'll still have the Thoraxe inhand, while the opponent can get the stage weapon from that stage. I call it a "carry over" trick. This would allow both players to duel each other with some drastically powerful and very different weapons.Needless to say, if the match settings are sett to five rounds and no time limit, you can pretty much explore every stage in one match.

The death trap in the Portal Nexus, if you finish off your opponent there is a toss off the platform into the Nexus pit where the opponent will be torn to shredds in an energy cyclone created by energies of the realm.
Since this is a composite stage, it will have many of the stage weapons and hazards that are in other stages. Also, the more areana's you unlock, the more this stage changes. It's configuration is random, I have only listed things that appear in the stage.