Anyone wanna help my ranked team with the problem we currently have?

im a supp main with good synergy with our adc. we're both plat. We both think similar and our mains have synergy. Another person, who is diamond 1 requested to join and i am completely ok with turning into a sub if it helps the team, but his choices aren't ideal synergywise with our adc. Of course, they could learn how to synergize with each other but that will take time. Should we pick the diamond or me to supp?