Who should I use my tonics on? Will be replacing lianna
If you’re sticking with the Left Wing position 100% kingston.
If you were contesting the Left Flank position it might be a different story & more competitive but in Left Wing it is definitly Kingston.
Also worth noting that Kingston hasn’t got competition for the FIghter Emblems (not as far as your defence goes anyways) whereas Zeline would be competing with Onatel.
Kingston. But the weakest link in your defence is that Ares flank, not Lianna.
Agree with Guvnor, if the only goal for your hero is to replace Lianna use Kingston.
That said, you already have a green sniper and Zeline would give your roster more diversity. I would go with her to broaden out your capabilities. You might consider making Kunchen your tank, removing Ares and putting both Lianna and Zeline on defense.
Lianna/Onatel/Kunchen/Zeline/Alice is your best net for that defence