You can achieve that an AI does not extend its village. For that purpose you set one and only one warehouse as construction site, that they cannot complete.
That are stockhouse 2 and 3 of the Vikings and the large stockhouse of the Saracens. (The reason is, that these warehouses need building material that cannot be fetched from a construction site,)
Besides that, you have to be careful that the missing material is not lying within reach of that AI.
(Stockhouse 2: pillar, stockhouse 3: pillar and brick, stockhouse large: brick and tile.)
If the player puts down the missing material near the construction site, the AI first completes the warehouse and then starts extending its village as usual.
By the way, you can assign tride agreements to that house; but the player cannot make use of them before the house is completed.
