With more and more records being electronic, it would be useful to add another column to the z39.50 search results which tells us what type of record the result is, i.e. physical or electronic or something else. This could possibly be pulled from the 006 (MARC) of the record. It would be helpful for libraries who aren't as confident in cataloguing standards but want to make sure they're importing the right type of record to their catalogue.
Maybe a possible workaround for now would be AdditionalFieldsInZ3950ResultSearch. We use it to display 336-338 which gives a good hint on the type of record for RDA records at least.