It can't be exactly as IP. I think you should not pair people for a terrain contest. The best entries go to round 2 and so on.
You could start with categories and each winner in a category goes to the next round.
If we have many rounds, it should start with simple pieces and go forward up to more complicated pieces of terrain or scenery.
You can also do it as a one shot contest such as Femme Fatale, TT or Rotten Harvest contests and if people are interested then think about a kind of IP contest.
BTW I am interested in organising it and why not being a judge (that would change).
If I have to enter such a contest it can't be before september.