Seems like the only option is to not include that field in the form, and then via script try to show / move where the subsidiary field is shown if using a OneWorld account

yes that’s exactly what I had to do. If you want to log a support ticket, maybe they will eventually fix it. it’s considered an enhancement

Any other roadblocks you ran into dealing with subsidiary fields?

if you have a custom role that has the subsidiary permission, it will also break when deploying via sdf. I had to execute my scripts as admin instead of a custom role to get around it

What a pain - I'm still confused why NS can't keep the custom subsidiary fields around for non-OW accounts (like they do if a customization is installed via bundle) - it works very well.

yeah i’m with you. the subsidiary fields are on the native records but they don’t let there be a custom record with a subsidiary field with sdf