Pugio Database Structure

[Praefectusclassis]

but could the pugio database not be arranged in much the same way as the tombstone imagebase, so that there could be different search criteria.

Yes Paul, that is possible. In fact, the system (goes for all databases) will go one further and allows you to combine criteria. So in the Imagebase you could search for all (e.g.) full length tombstones of Legio XIIII GMV.
In the Pugio database, you could combine blade & tang this way.