Been There, Done That. Only it was D&D. No one wanted to Dungeon Master. Someone has to be God though.
Problems I see with what you proposed:
a. You will need set times for rounds, otherwise folks will eat breakfast here, go to lunch then, and kibbitz and talk. Who knows when Round Three will start after the 4 O'clock beer.
A set schedule works for Western World persons, because we were raised Industrial Fashion with school bell schedules and such. Go with common sense and established times from previous tourneys. Round One 10 am to 12:15. Forty-five minutes for lunch and so on.
b. Rules disputes. Often, our
TO is at another table or across the room, so we ask the guys next to us. For you I suggest if the players can't work out a call or LineOfSight, establish that the players *next* to them make the Final Call. Establish that as TheRule.
c. You are going to need one Boss to collect and tally and pull tickets and make announcements anyway. You could appoint *that* guy by lottery.

Bring a d100 dice and have everyone dice off, lowest or highest has to do the Duty for the weekend.
d. That one dork who brought 4 Imp.Knights is going to be sitting alone for some time, until his Paper-Rock match up eye-balls him, laughs with all of his (melta-drop-pods, Screamers, 3 units of Fire Dragons, etc) and says, "No one will play you? I will." Set rounds and Swiss-style pairings (or any pairing system) guarantees everyone plays.
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Would I go? No, it sounds too loosey-goosey. I like the firm set times of a
RTT or
GT schedule. Now that
40k is in its 20+ years, a lot of players have families, It is easier to get your wife to sign-off if you've a firm time. But I'd chafe if drawing opponents was catch-as-catch-can.
I think you're going to have to appoint a judge. Maybe up the ticket price to get in and give a judge a stipend ($20? $50) to run the show.
Good luck.