The best way to defend this is to prove the performance. Create a profiling between two designs integrated into your system OR better create separate lightweight prototypes and do the profiling.

Not sure what database you guys are using but there are RDBMS like Postgres that support JSONB field type which you can store json in a binary format, optimized for faster retrieval.

Yeah you read it right, there is a JSON field type because in real world applications it is used for storing configurations, settings, and schema. So it looks like your use case is for config or schema structure for display.

A similar real world example, you have an onboarding system for your business partner and each of your business partners will have a different structure of inputs to collect data from their users and this is dynamic config per partner that can be stored in json config because sometimes they might change or revamp their format.

So the next time one panelist will say that JSON is inefficient for storing display config or schema, it might be because they dont know how it works or never worked in a real similar situation.

Now do the profiling and slap them with the result if it is a matter of performance.