Klemens Franz or his older brother, another Maximilian, would both be considered too small fish for a king's daughter. They were only GRANDSONS while Max III was not only the SON but he was the HEIR APPARENT to a bona fide crowned Holy Roman Emperor. Hence why Klemens only got a Palatine princess which was also due to a scheme dreamed up by the Elector Palatine Karl III to tie all the Wittelsbach branches together by marrying his eldest granddaughter to her cousin (Karl's heir presumptive), his next to the heir presumptive of Bavaria (Klemens) and the youngest to the heir presumptive of the Zweibrucken branch.
Also, Friedrich II is married to the daughter of the king of England, short of divorcing Mary (which he could theoretically request an annulment on grounds of desertion when she moved to Denmark to look after her nieces and nephew) but that's gonna piss GB off.