Keith will attempt to battle, but once he sees these employees are trying to protect the pokemon within the sanctuary, he'll attempt to reason with them. He'll point out that the aliens (UBs) obviously aren't attacking any of the trainers and pokemon who are not trying to stop them from getting to something within the Aesther Foundation and offer to protect any pokemon within the sanctuary.

However, if diplomatic efforts fail, he will proceed to battle these guys because he wants to help Buggy. His pokemon are still leveled up enough that he can continue using the beatdown strategy. Steel moves from Skarmory would dispatch of Sudowoodo, Kecleon and Stoutland can be dealt with by Houndoom spamming fire blast and dark pulse, parasect should go down with Arcehops' acrobatics, peilipper with rock slide, Lumineon by Gastly spamming hypnosis and ghost moves and Manectric with Vulpix via fire blast spam.