ESOP guy (and mctoe),
It is fairly common to restrict loans to certain sources and perhaps even allow the participant to select which source...for loan recordkeeping purposes. Nevertheless, I think that if the loan were to default, it would be proper to treat it as a pro-rata taxable event from all sources, therefore, very little, presumably, would be from basis. At least that's how I see it, and how I would prepare the 1099.
And there would be a 1099, as others have noted. I suspect the driver of this idea is trying to get away with something without committing tax fraud, or otherwise gaming someone's system, with the incorrect thought that somehow these circumstances don't require a 1099-R.