Play offs (Mexican Style)

Hello,

Could be possible to create a competition with one single group and Knockout?

Let me explain the rules.

• 18 teams
• The first 8 teams go to the playoffs (quarters)
  • the 1st place plays against the 8th
  • the 2nd place plays against the 7th
  • the 3rd place plays against the 6th
  • the 4th place plays against the 5th

• The last place goes to the relegation.

Of course, if there are fewer teams the qualification changes. 

• 19 teams
• The first 8 teams go to the playoffs (Semi final)
  • the 1st place plays against the 4th
  • the 2nd place plays against the 3rd

• The last place goes to the relegation.