Firstly it's not an event, it will be a service and secondly there has been no additional information about the service. No-one really knows. Currently you can sub twice and become an Inspector, so I would imagine that you would be able to switch this as your main once the time comes.
Were you able to in the last event? I don't know.... if not then, then possibly not in the future either.
The problem is that Judicator isn't available as a "first main". It's not a class that is available as a main at all. You need to have subbed all the other available classes in order to become an Inspector and then a Judicator.
I don't see any reason to change that class into a main and I doubt it will ever be posible since there are no skills available at lvl 80+ since that class can't go above lvl 80
Also, having no real skills (except the awesome Lightning Barrier and Final Form) is more a blessing in disguise as it means that those who decide to take their Judicator's to 80 (or higher than 75) can spend all their xp/sp on skill enchants for the overpowered buffs, as well as the dubious armour and weapon masteries.
Yup, that is correct - Judicator cannot be a main class, because the whole class is intended to be only a sub (and so has no 81+ skills). From the description of the event:
The Kamael race's Inspector and Judicator are subclass-only by design, so they cannot be changed into a main class. The Kamael have unique occupations that are directly tied to the character's gender, so when you change a Kamael character's class, the gender also changes automatically. For example: If your Kamael character is female and you choose to change your main class to a Berserker, your character's gender will change to male.
I do however wish the Inspector was an option for the switch to main option.
Why? Supposedly the Olympiad will now have a 3 v 3 format.
If that where to happen, Imagine a Nuker, EE and Judicator combo. That is just off the top of my head. I am sure you could put up a ton of juicy combinations to take advantage of the inspector Super Buffs and Debuffs.