125 million + Harper's 30 million = 155 million.
This is the only fact in your post. The rest is speculation. Another couple of facts are that the tax threshold is $206 million for next season, and the difference between $155 and $206 is $51 million, which is plenty of money to address the roster while staying under the tax.
Your point is disingenuous. The Lerners may decide to cut payroll and retool, and they may decide to sign Harper, but they won't decide to do BOTH. If they sign Harper, that means they will use the $51 million left over to address the other holes. If they don't sign Harper, I agree they will probably give Rizzo a budget far under the tax.
Frankly, I don't care either way. I'm just pointing out the extreme unlikeliness that they decide to sign Bryce for $300 million and then sit on $51 million in cap space so they can be third favorites in the division with one of the top three paid players in baseball.
As far as Eaton, I didn't mean "significant" as in "a brand new bullpen". I meant something that will help the team. He's still worth more than an A-ball prospect.