It would be very hard, but if push came to shove I'd have to say yes, and here are some reasons why:
Ever since Marquis went we have been desperately lacking a versatile swingman who could play multiple positions. Marquis could play PG, SG or SF each equally effectively, and he could defend all three just as well.
Tyreke Evans would give us exactly that, becuase like Marquis he can play either of those three positions.
Not only does this give us better versatility (the ability to match up with big or small lineups) but it also gives us great insurance in the case of an injury or foul trouble.
Between the two of them Evans and Cousins are averaging 32 PPG. Pierce is currently our leading scorer at 19 PPG and KG our second leading scorer at 15 PPG.
Evans (15 PPG) and Cousins (17 PPG) would immediately become our second and 2nd and 3rd scoring options. This takes pressure off KG who can now focus on defense and rebounding.
Rondo currently averages about 13 PPG, so that's a lot of extra offensive firepower gained by this trade...on a team that's drastically lacking offensive firepower.
By trading Rondo for Evans and Cousins, we've just fixed two of our consdierable size problems.
The first is size in the backcourt. We currently have 5 guards on this team, and 4 of them are 6'3" or under. That makes it difficult for us to defend larger backcourts like the Nets (Williams + Johnson). If we get Evans we can have a Badley/Evans starting lineup and a Terry/Barbosa/Lee bench. That means we have the ability to ALWAYS have a larger guard on the court.
The second is size in the frontcourt. With the addition of Cousins we now have four bigs who are 6'10" or bigger (Cousins, Garnett, Collins, Wilcox). This ensures that we never EVER need to have an undersized 6'8" Bass or Sully trying to slug it out at Center.
Much as I'd hate to see Rondo go, this trade just helps us in far too many ways, and given that the contracts match up we probably don't need to give up much (if any) more to make it happen. Plus we then have 5 guys who are 23 or younger, so our future is absolutely set.
To make things even better, we only need to give up one guy. We still have Barbosa, Lee, Bass, Sully and Bradley and Green. That means we still have a ton of trade chips in case we need to pull one more small move to round out the roster.