My favorite "+" for Elias was Flores, who could have moved into LF for the Marlins, with Yelich moving to CF (which he has played when Ozuna was in RF due to Stanton's injuries) which would make Miami whole plus a young pitcher. Since that ship has sailed, I guess offering some really good, but not elite, lower-level talent might work. Ian Miller + Luis Liberato? Something along those lines. If I really thought it was the difference in getting a deal done, I'd offer both Elias and Montgomery (Miami is looking for 2 starters) and something besides (Guaipe or JRamirez) for Ozuna + maybe Chris Reed, a former Dodger 1st round pick LH who is a reliever that could be stashed at Tacoma for a rainy day, and maybe a well-regarded lower-level 'spect.
I do fear that similar logic will apply and the Marlins will want Kivlehan to be the LF in place of Flores. I'd try steering them to Romero, Robertson, or Blash instead. Kivlehan wouldn't be a deal-breaker (though I would rather trade DJ than him) but I'd sure like to keep him. Montero would be a legit offer if the Marlins were an AL club, but alas. But maybe Baltimore, if they lose out on Davis, will give the Ms Tyler Wilson for Montero. Perfect park for Jesus.
So, musing over, without Flores, I'd offer Elias, Romero, and Guaipe or JRamirez and hope they take it. Adding Montgomery, with them adding some pen spaghetti would be the fall back.If I thought Sipp was out of reach for the pen, I might ask for Mike Dunn, a LH reliever of similar experience to Sipp, but not the recent dominance.
Then, to finish my plan for JeDi's execution, I trade DJ + Marlette to Boston for Sam Travis and Sandy Leon. Everything else is signing FAs - 'Kuma and/or Chen, Lowe, Sipp, and Oh. If Karns is who goes to Miami, though, my yen for Chen AND 'Kuma goes up considerably.