Let them mortgage their post-LeBron future on Cousins. All the more dysfunction to screw up their chemistry with.
As far as "basically" iterations of the trade go, I prefer thinking of them this way, helps me visualize the values better:
Kyrie for Fultz
Tatum and Lakers/Kings pick for Isaiah, Crowder, Zizic, and the Brooklyn pick
I would make each of those trades a hundred out of one hundred times. But as they really were seems riskier, more even and uncertain. This way I am certain I want Kyrie over Fultz, if that had been the deal, straight up, and I'm almost just as certain I would easily then trade Isaiah, Crowder, Zizic for Tatum, #1 overall on the C's board. The Brooklyn and Lakers picks are kind of a pick 'em value-wise, a wash.
You posted this somewhere else as well. I think I would break it down even further:
Fultz for Irving: Major win for Celtics, established star for unproven rookie with potential whose ceiling is to be as good as Irving but the probability is that he won't.
BKN pick for Lakers pick: This is pretty much even Steven (no Brad pun intended) so you can pull this out (kind of a least common denominator thing).
That leaves you with IT, Crowder, and Zizic for Tatum which I don't know what to do with.
I like the Tatum trade big time and I understand the Irving trade. It may seem like we overpaid for Irving but that is what you need to do to get that caliber of player. And I have no interest in Cousins at this point.
Lakers pick for Brooklyn pick is not even at all.
The Lakers pick needs to fall within a specific range (I think it's 2-5) for us to even get it. If it doesn't, then we get the 76ers pick or Kings pick. The 76ers could easily be a borderline playoff team in this garbage eastern conference - Sacramento will be bad, but whether they will fall bottom 3 is another question.
The Brooklyn pick is 100% unprotected, and looking at their roster I cannot fathom how they could possibly finish any better then bottom 3. The only teams I can see who could possibly compete with them for the wooden spoon are Atlanta and Orlando. Even the Kings (who have De'Aaron Fox, George Hill, Buddy Hield, Zach Randolph, Willie Cauley Stein) have infinitely more potential then Brooklyn does.
Basically the only way Brooklyn could possibly fail to fall bottom 3 is if D'Angelo Russell suddenly breaks out into a Damian Lillard calibre superstar and carries the team better then Brook Lopez could, which I seriously doubt will happen.
Otherwise that Brooklyn pick (which has potential to be as high as #1) is easily more valuable then a highly protected Lakers pick in the same draft.