Lol! It seems like this may not be the first time you've thought about this.
As for the original topic, the fact that it's in an open space theoretically helps the strikers, but the lack of gloves and the fact that you chose heavyweights for this match-up means that most times through this is going to go to the MMA fighters. Watch just about any HW boxing match you will see quite a bit of clinching or at least the fighters getting into range where they could clinch.
If any of those HW MMA fighters gets into a clinch with any of those boxers even once it's going to be game over for the boxers (whether that be a thunderous takedown into the pavement (and trust me, getting taken down on pavement, especially if you haven't trained correct breakfalling extensively, which not too many boxers do is a lot different and less forgiving than getting taken down on a mat or in a padded ring) or a knee borage from Overeem).
And honestly, it's a lot harder to land that one clean KO punch on an incoming grappler than untrained people (or even boxers who don't have experience trying to do so) think. It can be done, and the open space does make it somewhat more feasible. But I wouldn't bet the farm on it. And if you aren't right on the button then:
1) the grappler is on and you are going for a ride
2) you may break your hand (especially since most pro boxers always have their hands wrapped, or wear gloves to protect them, or both and therefore aren't used to hitting hard things barehanded), which would leave the boxer with only one hand to try to KO the MMA fighter
3) both may occur
Now, had you chose a HW like a prime Tyson (who was extremely explosive and fast, hand legit one punch KO power in either hand, was mobile, and had some street violence experience), a prime Roy Jones Jr (who again could KO you with either hand and was unbelievably fast and mobile), and a prime Roberto Duran and picked more striking based (or at least not as accomplished of grapplers) MMA fighters like Tim Silvia, Rich Franklin, and Anthony Pettis I would have given the fight to the boxers (as stylistically they would match up better).
Remember that styles make fights and people fight, not systems.