Dang. I was debating what was going to be worse to place pseudoaxial... the tert-butyl or the TMSO group. Well I guess silicon is quite fat, and thus I have to agree with Heory's transition states.
Heory: After the organocuprate does the michael addition we're left with essentially a fancy metallated enolate. The metal just happens to be copper here, but I don't see any reason why this metallated enolate shouldn't react similarly to others (potassium, sodium, magnesium, titanium, boron, etc.). So I may be missing something but I didn't think it was a problem at all to imagine the copper enolate attacking another carbonyl functionality.
So what's the others parts to this problem???