Can we package something for Ellis and make salaries meet? Certainly. The question as you state is whether or not we can package something interesting for both parts.
If Golden State trades Monta Ellis, they do it because they can gain an impact defensive big. They do have the possibility of trading Ellis, while still not losing too much impact in their backcourt. But who would we have, that could fit that description?
They need someone who's athletic and active on defense primarily. Garnett is certainly a defensive presence, but he's not what Golden State is looking for at all, nor someone the Celtics would think of moving. Outside of him, I don't see anyone fitting that description on our roster.
Could Perkins have done it? Possibly - But going down that road is futile, and highly speculative.
I think GS will try to strengthen their core by signing or S&Ting for the likes of Bogut, Dalembert, DeAndre Jordan or possibly put a lot of faith in someone like Ty Thomas, who could probably be acquired for relatively low value at this point.