...it tends to work as 'author's choice'. I personally do use capitalization minis, but I co-write with people who don't (mostly for convenience, I think). And what we tend to do here with published missions, unless there's something very problematic in them (generally not to do with minis, in my experience) and they were just published pretty recently, is to leave them be (unless the author is around and wants, of their own volition, to change it).
If the author of the first Deltora Quest mission (which, heyy! I used to read that! I don't remember much about it, but it was fun!) made the decision not to use capitalization minis--that was their choice, and we can't change it after the fact. Or, at least, it certainly seems like an extremely rude thing to do, especially without talking to the author (who, it seems, is Caddy-shack, which is awesome, I have a mission to read or reread now!) about it and getting their view on it. If you want your agents to have Deltora minis--why not get Permission and write a second mission set there, which establishes what the minis are? It's a good deal more polite, not to mention more usual for the PPC (as far as I know, old(er)bies can feel free to confirm or deny), and, really, is more polite than suggesting even in-universe that Agents Cadmar, Maria, and Mark just happened to miss a mini. Especially since you're not, to my knowledge, working with Caddy-shack on this (or even discussing it). How would you feel if someone did that to your agents, over a decision you made? If someone's agents were introduced together with, say, a mini blinking out of existence because their author didn't agree with you that capitalization minis should be used?
Or, to make this a bit more to the point: pretend you've written the first mission for a canon. You chose not to create the new mini type because you don't use capitalization minis, or chose not to for this mission. Later, someone decides--without talking to you first--that they don't like this decision you made; instead of writing their own mission to that canon and creating the mini-type, they have the capitalization mini appear in HQ, with the acknowledgement that that canon suddenly has a mini-type, and say outright through their agents that your agents must have missed the mini or something. Would you seriously be okay with this? Would you seriously not find this rude, or potentially lazy (in the sense that this person could have gone looking for a fic to mission that uses the same mini, if they were attached to using that particular one, or could have had their agents be the first to officially meet said minis, which could be pretty exciting to write and to read)?
That's my take on it: it seems rude, quite unusual, and even rather lazy to create a mini-type--and a mini--this way. Capitalization minis are not used by everyone; retroactively editing around someone else's mission in this way seems rude, especially since it feels kind of insulting to the agents who did the mission; and the more polite--and, to my knowledge, more usual--thing to do would be to simply write a mission and create the mini-type yourself that way. And I'll stop there; I think I've said everything I want to, and have even summed it up again at the end. Night, all.
~DF