Ian Sullivan, could you take a look at these obs_* package dataset type changes? I think you were the last person to attempt something like this in obs_lsstCam, and you're certainly in the best position to check dcrCoadd things.
On that note, there are also some dcrCoadd definitions in obs_decam that look suspicious to me, but I'm not sure what to change them to (unless it's to delete them so the obs_base ones are used). I have not made those changes on this ticket but would be happy to if you can point me in the right direction.
I am under no illusions that this fixes all problems with dataset type definitions, but I didn't want to change anything that could be backwards incompatible (i.e. changing a template definition) unless I was certain it was already broken (aside from obs_lsstCam, where I'm explicitly trying to get things in shape for better future compatibility).
I'd recommend looking at these commit-by-commit.