I don't want to be mean, but you know, there is the word "teen" in "teen titans".
Proposing a character is okay, there's a channel dedicated to it on our discord, but there's rule to follow, go check the discord for it if you wanna to, we only add character to our poll from there. (One of the rule being "18+ only")

For information, Raven and Starfire appeared already on our poll, the adult version of them, from DC Comics, not their teenager version.
(They usally don't get that much vote though)