Blackmon is not that great. Wildly overrated, so he'll cost more than he's worth. Pillar is a better overall player than Blackmon.
A trade for CarGo makes sense, but it will probably cost one of Travis/Stroman/Sanchez
A deal for Blackmon AND Gonzalez would probably be something like Pillar + Stroman/Sanchez. Colorado would definitely ask for one of those pitchers.
You might be able to negotiate them down to Pillar + Travis + Foley or something.
It's really hard to speculate, because different front offices can overvalue/undervalue certain players.