You did well, as this seems to be a case for the support.
Anyway, if someone else already had to do something like this, I hope they will see this post and bring how they worked this.
I still think that extending a model that is already in production for quite some time should always be done through new entities/extensions, to avoid messing with the data and have this kind of problem.
The new entities would be empty and being extensions, would be a matter of doing a simple join in the places where you need the information.
If you receive a solution/workaround from the support, please, let us know.
Cheers.