Oh sweet, yeah the OOC is looking great!
If I have to be REALLY picky though, there's this little detail that might stand out but is otherwise pretty irrelevant if you're just looking for a casual experience. Either way, it might or might not be a good idea to get it sorted out just in case for aesthetic reasons. What I'm talking about is the failsafe. I apologize in advance if I get some of my facts wrong seeing as it's been a while since I last read /Apocrypha, but I think the failsafe needs to be manually triggered by a mage before it activates, and will most likely remain dormant if left untouched. Then there is the issue of the Lesser Grail itself, which has previously always been provided by the Einzbern. With Illya failing to claim the Grail in the 5th War (depending on which route you are looking at), they are likely to have given up on attaining the Grail altogether and isolated themselves from the world, which begs the question: who will provide the vessel for this Holy Grail War?
Fortunately these two problems might cancel each other out.
The Einzbern are likely to refuse to participate in a Grail War ever again, that much is known. Thankfully it's the Greater Grail that is responsible for the summoning of Servants however, not the Lesser Grail. This means that an Assassin Servant can be summoned prematurely by one of the participants or by the Mages Association and be ordered to infiltrate the Einzbern household and steal an early prototype of the Lesser Grail Vessel. After all, it was only during the 4th and the 5th Holy Grail War that the Grail Vessel was fashioned after a living homunculus, whereas in the 1st, 2nd, and 3rd it was simply an inorganic cup. By stealing an early prototype of his Cup we'd once more gain the ability to collect the souls of Servants after their defeat, and behold, the Holy Grail War is up and running again. Once we've come this far, it'd be easy to say that since the cup that was stolen was an early prototype, it didn't have the failsafe installed yet, so it naturally summed 14 Servants to begin with, without the need of manual activation of the system.