The OKC starting lineup is not the problem. Yes AB is a big upgrade on Roberson, but that doesn't solve their bench issues.
Kanter works best off the bench, where he can provide second unit offence (its not like the starting 5 needs more scoring). The problem is the rest of their bench is terrible.
Waiters is streaky at best, Singler has one good game a season, Collison is a solid vet, but hes past his best, Donovan seems to think Randy Foye is a PG, when clearly their best option to back up RW is Payne, but his defense isn't up to scratch, and the rest barely play.
OKC needs to find some solid role players that actually fill a need, the problem is their owners are adverse to spending $, so they will never get there.
Trading AB for Ibaka makes sense, then signing Gasol (in hindsight he should have signed with OKC in the first place) would fill Ibaka's spot. Robinson can come off the bench with Payne and Kanter, Then they would need to get rid of Waiters, Morrow, Foye and Singler (easier said than done) and sign some more capable guys to replace them...
Then they have a good shot at the West