I doubt this is an upgrade over Bass and even if it were, it would be a mild one at best. The Celtics would be better off looking for a third big behind KG and Bass who is an upgrade over Wilcox and Collins than trying to upgrade Bass and still have to play Wilcox and Collins.
Ideally, I'd want someone who has the upside to be a possible good fit in a big man rotation next season with KG, Bass, and Sullinger.