Non tendering JBJ or trading him gets us to the line. Trading Betts is one plan. Trading JD is another. Trading both would be a total rebuild, but even that plan has merits. Trading Price and/or Eovaldi won't save us much as we'd have to take salary back or give cash.
Let's take the trade Betts plan. Yes, if we trade him, we'd be $28M under the tax line, assuming we don't get anyone higher than min salary in return. Then in theory, we can spend $28M a year on FAs to make us respectable in 2020, but I'd only sign players that look to help us beyond 2020. Some would be one year deals to allow us enough space that when JD opts out after 2020, we'll have enough space to sign Betts. (We should be able to go back over the line after the 2020 reset., even if JD does not opt out.)
I don't think it's that complicated to understand.
Yes, the fams paying for season tickets probably prefer to see Betts over Ozyuna and Smith or the other 4 I suggested below, but we'd be better positioned for 2021 without a doubt in my mind.