If DeAngelo believes the Rangers are going to offer him like 6M for a year or two, and some team offers him 7-8M longer term likely up to 5 years, yes I do believe he would maybe sign it, and yes I do believe some team may offer him that even if it costs them a 2021 1st, 2nd, 3rd. Teams are allowed to talk to RFAs prior to July 1st. Agents of current Rangers are allowed to ask the Rangers management what their offer is.
Arbitration does award term, in ADA's case since he has more than 1 RFA year left, it depends on who filled for arbitration. The party who does not fill gets to select a 1 or 2 year term award.
To avoid going to arbitration the team is going to have to offer about what the award would be for anyway. Which is where comparable contracts comes in.
Those comparable contracts can be any contract a RFA signed. It does not matter if they were 1, 2 or even 8, 13 year deals, all that matters is what those contracts had as salary for any RFA year(s) within because it's salary arbitration and comparing RFA year(s) to RFA year(s)
The Rangers risked whatever they did, ADA was forced to risk what he did because the Rangers used up all their cap space instead of using it on him. That usually does not lead to the player taking any sort of discount in future deals.
The arbitration process is non negotiable should it reach the award stage, the team can either sign the deal or let the player walk (at least in this case as the award would be over the threshold for the team not to be able to walk away from)
I know you will compare the players, yet if you read this it may give some insight into how arbitration works.
Weber lands record $7.5-million arbitration award
As you can see, they compared recent contracts of players who had both RFA and UFA years included in their deals. They only used the RFA portions to get a salary comparison. Also note Weber at the time had two RFA years left.
Nurse two RFA years, his salary in them is 5.6M, yet that was with him coming off a 41 point season
Chabot extended, his RFA years go anywhere from 4 to 8M in salary, yet they average 6.5M, coming off 55 points.
Morrissey 8M in his 2 RFA years.
Trouba in his last RFA year is at 12M in salary.
Those are the most recent comparable contracts that have RFA years in them.
I know which two the Rangers would use as comparable, and I know which two DeAngelo would use.