Just took a closer look at the DPDD section on DIAObject, and here's a more thorough report on how I think DRP DIAObjects ought to differ from Prompt ones:
diaObjectId: could and probably should just be an objectId (all DIAObjects will be Objects, but not all Objects will be DIAObjects).
radec, parallax, pm*, psFlux*: Object.ps* fields should usually provide better-measured versions of all of these quantities (more optimal estimators, at least in uncrowded regions), but I'm sure we'll find cases (crowded fields?) where these are more robust. And having two very different ways to measure these quantities is good for diagnostic purposes.
fpFlux*: DRP is currently slated to do both difference image forced photometry and direct forced photometry (though I believe Robert Lupton thinks the former will almost certainly be uniformly better, and I tentatively agree). As long as these are a mean of the difference image forced photometry, they're quite useful (see https://community.lsst.org/t/data-model-for-variable-sources-at-time-of-data-releases/2695/5) as an indication of the offset between the flux in the difference image template and the flux measured in all epochs. We should probably document this as its main purpose in DRP (I think this is not a role it can play in Prompt, where the forced photometry doesn't extend to all epochs and there are no deep fluxes to relate to anyway). I don't think a version of this that averages direct forced photometry would be useful, unless it turns out to be a diagnostic on how well we can "project" coadd deblending results to single-epoch images when we do the direct forced photometry. We should also definitely move these columns to Object in DRP, so that Object includes all quantities derived from ForcedSources and DIAObject includes only quantities derived from DIASources, and so we make these measurements for Objects that are not DIAObjects.
lcPeriodic, lcNonPeriodic: Unless the DIAObject quantities are measured from DIASources instead of difference-image ForcedSources (not clear from the text, but I think these should almost certainly be measured on ForcedSources), these are exact duplicates of the quantities in the Object table and need not be repeated here.
nearbyObj:* if we just use objectId instead of diaObjectId above, these are not needed at all. If we still have a separate diaObjectId as the primary key, we should only need one objectId here because the association will be unique, and we should just call it "objectId" or maybe "derivedObjectId" instead of "nearbyObjectId". In either case I don't think the distance or association probability is meaningful, as the Object will have been created from the DIAObject.