Just entertaining an idea here, specifically for the Summer Nationals......
How 'bout utilizing the referees on mandated days-off as test-fencers?

They are certainly knowledgeable about the rules, applications, and more importantly, the day-to-day scenarios that arise which challenge the working referees themselves. Plus, they have a demonstrated capacity to detach themselves from the emotional/social context (in this case, that of the apprentice referee) and perform their duties as instructed for the duration of a task..... i.e. remain mature enough to create convincing situation rather than making a joke out of it, which would of course greatly change the nature of the test.
So given the appropriate training (specifically geared for this role), and incentive for availability (they already have per diem for mandated day-off, so a small additional service fee), this could serve as a standardized, highly convincing test of apprentice referees who have no viable means of local testing.
This also creates an environment where a wide variety of rules application scenarios can be introduced within a relatively short period of time... In addition, this creates a safe environment for development of very basic level apprentices without too much "damage" to the competitors who have made significant investment to come to the National Championships.
Additionally, this would also serve to promote healthy activities for full-time referees!
Not that I have anything against the policy of MANDATED days-off for referees working at Summer Nationals or anything....

Really.... Honest....

But we're going to be gathered in the same location for 10 days once a year anyways. Might as well look for ways to add some variety.