They'd need to buy the model from a pro gunpla customiser, probably for a good amount of money. A model straight out of a store shelf would be no good against these guys. During the first season we already saw that it took a good amount of customising experience, innovation, and imagination to make a model that would stand a chance. Despite having built models since before he could run, Iori needed a couple of eureka moments to make one that was barely sufficient. Meijin and Aila used models built by crack teams of engineers. Mao had a whole school of gunpla builders' accumulated experience behind him. Nils is a fricking genius and nuclear/quantum physicist or whatever.