Detroit would have to include a lot more than Monroe for Rondo since he is on his rookie deal.
If I'm Danny and they want Rondo, I want Drummond in return. However, again, the Pistons would need to include more than just AD
If the Pistons offered Drummond straight up for Rondo Boston would accept that deal in a nanosecond. Boston wants to tank and they won't be able to do so if Rondo is still on the roster - Drummond + whoever they grab in the lottery would give them two blue chippers to build around long term and they would still have a bunch of draft picks going forward.
As for Detroit, the Josh Smith signing is intriguing, but probably not one that's going to benefit them long-term. If they plan on playing Smith at the three, they'll have created floor spacing hell on offense. If they plan on going with more of a traditional NBA frontcourt, they're going to stunt either Drummond or Monroe's development. On the other hand, Detroit would be a menace to go up against on the boards and potentially well above average defensively with an alignment of Smith, Monroe, and Drummond. Frankly, I'm not sure what they think the end-game is here: why not just suck for one more year, grab another blue-chipper in the lottery to pair with Monroe and Drummond, and then go from there? You have to wonder if this is a matter of selling tickets.