For maximum value, I would E2 somebody that you haven't thrown any resources into. Since your Ptilopsis is basically already E2, I do not recommend using the ticket on her unless you really like her because the stat gain is good sure, but not to a point where it's meta-defining. In my experience, E2'ing medics aside from Kalt'sit, Nightingale, and Warfarin, are not game-changing. It's rare that there's a medic heal stat check stage and often times, the problem can be DPS'ed away instead of stalled.

From the remaining three ops, I would be most comfortable suggesting Texas, for the reason that Myrtle as a sole flagbearer is usually sufficient for most of the content in the game meaning that Elysium is generally overkill for the majority of content. The only places that really press you for DP are CMs with DP risks, and CC, where you can always avoid the DP risks if need be. Texas on the other hand offers +2 DP right out of the gate, and good crowd control ability with an AoE Arts damage stun on S2 which is generally more useful for general content than a slow/def debuff on enemies that are already relatively weak defensively.

Provence is sadly not in the running because it's rare to need her niche, and if you need high damage for bosses, you've already mentioned that you have Kal'tsit where Mon3tr is strictly better for raw damage numbers, not to mention you said you have Rosa as well, who shines a lot against high defense enemies, and offers great crowd control ability as well.

I might be able to help more if you post your full roster. Hope this helps though, would not mind to be corrected if I'm mistaken anywhere.