It can be a great situation. It all will come down to how the costs are split.
I do pop-ups at a brewery and it's worked well. A few other breweries in the suburbs here have partnered full time with pizza vendors and it seems to work out.
Sounds like you have a trailer based catering/pop-up operation already.
For me, since it's just a side hustle I'm fine counting on the brewery to be the draw. I'm planning to start moving to it being more full time in the next 1-2 years. The part I'm considering is how do I grow the 'pizza' business seperatly. Adding sales paths/segments like- pick-up, on-line ordering, differnt styles, highlighting vegan/GF options, 3rd party delivery. The numbers (for me) don't work for a full time operation if it's only the brewery bringing the guests.
Also just my experiece at pop-up- I push for higher guest check by selling only larger pizza targeted to couples, families, and groups. The pop-up market here is all 10"-12" quasi-neo pizza intended to be 'personal' size that sell for $10-14. From what I've seen guests still only order 1 pie for 2 guests.
As to slices same issue- guest check too low.
My prices are $20-25 for pies that serve 2-4 guests. I prefer to sell less pies for more $. Not only is it better for me it also attracts the guests I want- couples, families not single guys hanging out.
The market here for non-pizza pop-ups/food trucks is $12-$18+ per entree. I seen no reason why pizza shouldn't be in the same range.
I'm the lone pizza pop-up guy in the area with this model, so maybe I'm wrong. Your milage may vary.
Andrew