Even agreeing with you in that the different rules have an impact in the fairness of the result, I think the main difference between XBall and 7man is that luck is less of a factor.
Example: at Barcelona Open a novice team won Shockwave. Shock's guns were not working and they had bad luck during that game. In a XBall match they would have had 10 or 15 more points to recover, in 7man (it was 5, but I think my point is still valid ;D) they couldn't.
That said, it's true that in 7man the rules and the reffing sometimes let the cheating team get an advantage. A clear case is the classic "I'm hit so I'm running" where cleaning up the mess is next to impossible. You can apply a 2-4-1 to the runner (I've never seen this applied, btw) and reinstate as many players of the other team as you think, but there will always be someone (probably clean) running up the other tape, taking advantage of the fuss... how do you fix that with the current set of rules? You can't. Finally, the cheater team got an advantage and probably the game.