I think that trading Cousins is a very bad move and here's why- you talk about trading him and going for a rebuild, there are a couple different ways you can do rebuild:
1. Blow everything up and start over through the draft (imo what most people mean when they say rebuild)
:
If you go this route you'll trade DMC and the other veterans you can get value for (Gay, Rondo, DC and KK most likely- which have limited to very limited trade value), and build through picks you acquire and your own high lottery picks via tanking.
Besides the fact that going this way means that your team will suck when you open the new arena, and that you will no doubt add to one of the league's longest playoff droughts- the conditions we have now aren't suitable for this move.
Our young talent/long-term players in that case are WCS and Ben- both showed some promise (WCS more so) but those are not exactly pieces you want to build around as your main cornerstones.
The far worse part is that you have no control over your own pick, you can't win the lottery in 2016 or 17 (since if you do the 76ers will get it) which limits your options, (Minnesota would look much less intriguing without KAT) and while this year since the 76ers suck the swap isn't that big of a deal it can change in 2017.
Either if the owner gets tired of the "process" or if they get enough young talent to build on this draft since they hold OKC's and Miami's first rounders along with the Lakers top 3 protected pick which can be REALLY good (Simmons and Murray/Dunn is completely possible for them) and then they may outsource their tanking to the DMC-less Kings (like the Celics-Nets situation). and let's not forget the 2019 unprotected pick we owe them.
So basically you will try to build through the draft, when you don't control your pick in 3 out of 4 years (and in the last one it's simply not yours).
So that kind of rebuild is out of the question.
2. Acquire some good players with young talent:
This is your move if you think that DMC is
a problem and if you'll gather some decent players in his place, including some young players you can build around, the team will be better off.
Let's give some imaginary deals in that nature:
PHX- DMC for Markieff, Len and Booker
DEN- DMC for Faried, Nurkic and Harris
ORL- DMC (and maybe DC/Ben) for Vucevic, Gordon and Hezonja
This trades give you some decent present and a hopefull future, if you are going to trade Cousins I'd like it to be in this way (and those trades are imo exactly what Karl would have wanted).
None of this players are even near DMC's level (Vucevic is the closest, but he is far far away),
but you can be competitive with this moves- however I believe that your ceiling will be lower than it would be if you could make the roster (and coaching) adjustments needed.
3. Trade a star for a star:
This is your move if you think DMC is
the problem and would like to replace him for a lesser star with what will be framed as "better attitude" or a player that "fits the style of current NBA".
Some imaginary deals in that nature:
CHA- DMC and DC/Rondo for Kemba and Al Jefferson
PHX- DMC and DC for Bledsoe and Tucker
This kind of deals limits your upside and are harder to find.
In conclusion, trading a 25 years old top 10 player is almost always a bad call- especially if he is on a bargain contract that isn't about to expire. you do that only if it's your only option (Minnesota knew that Love is about to walk), and that's not the case.
If you add rhat we are in a bad position to rely on tanking and that we have very limited young talent to build around- it's really hard to find a situation in which trading Cousins is the right move.