For someone who is all about avoiding long term contracts because the back end could get ugly, you are really changing your tune here. You justify Harper based on the reduced AAV which is fine (though doubting that is exactly what you said when he and Turner each signed), but you completely avoid the issue of the opt-out. If Harper has a good second half this year (say 900 OPS and playing the field again) he would have a significant market out there. He would have 8 years and $196 million left on his contract. He could easily beat that potentially.
And there is a chance that the last 4 years of his current deal will be very bad.
If he leaves it "leaves a hole". Well then you sign someone else or produce a prospect. That is how it always works.
You just can't have it both ways in your argument. If these long deals are so bad, then an opt out protects against the risk. It does not require the team to re-up the player at an even riskier price like the Nats did with Strasburg. You just let the player go. And sign Ohtani if you can.