I don't think we reset in 2020. I think we look at 2021 to do it.
Your 2020 numbers miss a few things.
$15M for player benefits
Arb raises will be on top of this year's arb raises, which will be way more than $20M from the 2018 contract numbers.
You mention we will need 1B, DH and SS, but what about replacing Sale & Porcello?
Here's how I look at 2020:
Luxury tax dollars
31 Price
24 Betts (last of 3 arbs)
14 JBJ (last of 4 arbs)
14 Pedey
12 ERod (3 of 4 arbs)
6 Vaz
6 Wright (last of 3 arbs)
5 Barnes (2nd of 3 arbs)
5 Beni (1st of 3 arbs)
3 Hembree (2nd or 3 arbs)
3 Workman (last of 3 arbs)
That's $123M for 11 players. We need 14 more at the ML level and 15 to fill out the 40 man. At minimum cost, that's $145M in salaries plus $15M player benefits= $160M. That's with replacement level players in all open slots.
That leaves $48M to upgrade some of those 14 slots with better players. Devers, Johnson, Velazquez, Brasier, Poyner, Lin and maybe a couple others could do nicely, but replacing Sale, Porcello, Eovaldi, JD, Bogey, Moreland, Pearce, Nunez, Holt & Thornburg while staying under the luxury tax is frightening.
I don't see it happening until 2021, and if we keep many of the players listed above at more than a 1 year deal, and we want to reset in 2021, then bye-bye to Betts & JBJ.