It seems to me that Shawn is joking about being Juliet's lover and the possibility of her cooking him bacon in the morning after they sleep together.
When he says "I'll get a title bump... something like First Lover in the Nighttime," he is saying (roughly) "If I help you get promoted, you'll declare me the best lover."
This is not the first time Shawn has used the phrase "lover in the nighttime." In the final episode of season 6, "Santabarbaratown", he jokes about him and Gus being "lovers in the nighttime... (like The Insiders except even more gay)".
When he says "Maybe a little bit of bacon," he is probably referring to the practice of a lover making breakfast for their partner who slept over.
The character Shawn often references bacon. I do not think this is a play on words related to the convention of calling law enforcement "pigs," as suggested by @Icy. Such a play on words would be inconsistent with the reference to being lovers who slept together.