It is definitely worth considering extending the current contract to also be insured as an owner. For example, condominium owners can be drawn into legal disputes for many reasons or even have to initiate one themselves. It may become necessary to challenge resolutions of the condominium owners' association that one considers unjustified – for example, because they do not comply with proper administration.
One can also join an interest group that also offers legal protection (e.g., [Haus & Grund Eigentümerverein]).
However, these are matters that require legal advice in normal operations.
ARAG also offers a real estate legal protection insurance that includes builder’s legal protection (included in the premium package):
Builder’s legal protection insurance coverage exists for the assertion of legal interests in disputes related to the purchase of a building plot, a conversion, or new construction (waiting period 6 months). Examples: disputes with the building permit authority, the developer, the architect, or the craftsman.
However, at this point it is already a bit too late (because of the waiting period)...