Consider a cap on numbers of hens per plot. We also only allow 20% of plots as livestock plots. Our rules for livestock only allow hens and pigeons. Decide what you can allow and ensure it is drawn up in the contract. Ours is written that all other livestock is excluded.
Draw up rules regarding cockerel's. One or two plot holders have had to get rid of certain cockerel breeds due the crowing at 3am in summer months waking people in nearby houses. We have had the environmental agency on our backs due to some plot holders noisy cockerel's.
We also have a maximum permitted size of a chicken cree so that it does not dominate the plot. Some plotholders who don't want to cultivate in the past have had to be reigned in by the council as they have turned over 1/2 the plot into a chicken run......

Our rules also have a policy on neglected livestock. Additionally, if a plotholder is evicted, they have 28 days to remove livestock after which we call in the RSPCA who take come and take the livestock. This has never happened yet, though 2 plotholders have had complaints made against them and written letters followed from the RSPCA due to neglecting their livestock.
Finally, any plot holder who wishes to keep livestock must first apply in writing to the town council indicating how many hens they intend to have, size of the cree, and a sketch map of their plot showing the location of the run. (This is to ensure the cree is erected in an area of the plot that will not obstruct sunlight from neighbouring plots.)