It would make sense that Oberon thought of Cupid to help Titania fall in love because Cupid is known for helping people become in love with a shot of an arrow. (or powers)
Explanation:
When Oberon thought of Cupid the idea pop up to Cupid could help force Titana to fall in with the beast thinking that Titania couldnt be forced any other way.
it might change the plot of the story by the character is at one place and he/she lost or forgot something so they have to go back an get it or find it.