I can share some experience. I story-guided the Normandy tourney for my troupe a few months ago. I was ambitious and I wrote down whole tournament elimination trees for each event, after deciding which teams were most likely good at which events. I admit it was a challenge to run, and we did run into a few problems.
Our PC Covenant had 10 magi, and that gave them starting points meaning that any significant victories would put them among the 7 first positions with a lot of vis winnings. I also did adjust the rules so that quarterfinalists in the most major events would get a few points. You may consider those issues when balancing hope in participating VS game balance/realism.
Second, we discovered when playing that some rules need clarifying:
Hastiludium: Can a shapeshifted magus be the mount? Can you just mundanely carry the mount and the rider on it?
In play, it quickly became very complicated to adjudicate, with lots of magic being cast. Would NPCs be fooled by rego imagonem that moves the arrival line?
Joust: How much magic can be cast in advance? Can it be cast by non-participants? How about enchanted items: does the jouster have to enchant them himself?
I made this a "best 2 of three" contest, using the 4th ed + Ordo Nobilis brawl/unhorsing rules.
The players quickly thought of the non-metal, non-wood weapons trick. So quickly that the NPC specialist's "secret tricks" from L&L seemed lame and obvious!
Dimicatio: We ran into rules trouble here. We tried to clarify the effect of subtle/quiet/silent casting on the difficulty of recognizing a spell. We ended up applying this house-rule formula:
Perception + MT + spell magnitude - voice/gesture penalties (even if a virtue cancels them for the caster) + stress die. We used an ease factor of 6.
It did not work well at all, since it quickly became a totally silent/invisible battle of spells that were rarely recognized by the opponent, and the rounds repeated endlessly.
However, we did like another change we made: that you had to use different spells from round to round.
MÃªlÃ©e: You really have to clarify what kind of attack success is required to prevent a character from an action like diving towards a ring in the sand to rub it...
For the "Host's choice" event, we had a treasure hunt that was fun. The magi had to collect as quickly as possible a number of tokens that each required different talents or magics.
One was glued on top of a high pole. One was invisible and at the bottom of a pond. One was hidden in a puzzle-box that required int + legerdemain rolls. One was in the middle of a ring of flames. One was unlocked by an enigma written in cypher (which required quickness + artes liberales to decipher). The last one was protected by a chained griffin that you were not allowed to injure.
That event was great fun for the troupe!
As a few final thoughts, I wish I had used your approach of not trying to simulate the whole affair for my ambitious beginner magi. If they don't stand a chance at anything, it's frustrating to play out repeated failures, or else you get soft and they win more than their share...
Good luck on your tourney!