no to both Serperior and Raticate. Serperior just doesn't hit hard enough, and we already have Sceptile and Whimsicott (when it drops). We have no need for covering Serperior as it is.
Rat is frail, slow, and is outclassed by Pokemon like Swellow and Tauros, both of which are mediocre at best in UU. So no, Rat is no good.
"Hmmm... a name for this plan..."