Longinus:

Got it, I was already asking for a lot when merging two origin stories into one so I wasn't too sure about that one to begin with. I'll stick with the original lore then, which obviously disqualifies him from having Battle Continuation. His CON Stat was likewise a reference to the anecdote with the lion and the cave, so I'll drop that down to C as well.
In regards to his Magic Resistance, this is my unfamiliarity speaking, since I assumed that his nature Class Skill of Magic Resistance together with his status as a Saint would boost it to a higher Rank, but if that isn't the case (especially since his lore fails to mention any feats regarding magic) it makes sense to drop that down to C Rank as well.
As for his HP Recovery, I meant it to be less a passive Skill and rather the act of curing oneself through the use of Christ's blood that is excreted by the Lance. His blood was associated with many miracles after all so I assumed it to act as a cure and healing agent for most curses and ailments below mythical and sacred level, essentially afflictions that reside within the realm of man and beasts. Then again, if this overcomplicates things, it's fine to turn Christ's blood into a healing agent only (in regard to physical injuries alone).


Mitsuki:
I guess I was all over the place when writing her Biography so let me clarify, it's not that it was particularly the research that made the Mages Association aware of him, but rather the result of it. Admittedly, the fact that Dead Apostles were spawned as a consequence and forced the Association to take care of the mess is a large plot convenience, but it was ultimately them that caused the Association to act, not the nature of the research.
In the case of her Origin I might have made a mistake based on a misunderstanding. I assumed that the likes of Kiritsugu and Shirou also had their Origins awakened due to the nature of their behavior and abilities, but the way you talked about Mitsuki's Origin seems to imply otherwise. Though not directly manifesting in his abilities (Origin Bullet is more of a tool than an ability), Kiritsugu's life is evidently shaped by his Origin, and in the case of Shirou it's even more obvious due to the existence of Unlimited Blade Works and the fact that his body would sometimes literally transform into swords to prevent him from dying, for better or for worse. I had assumed that their Origins were awakened much like Shiki's and Lio's were, but I guess I was mistaken after all? In that case, would it be possible to negate the "awakened" aspect of her Origin (seeing as I was clearly misunderstanding what it meant to have an awakened Origin), yet keep everything else unchanged?
In regards to her age, Mitsuki was mostly a character created to give myself a chance to work outside of my comfort zone by writing about a character outside the average age range I usually use. I can see how it might have been impolite of me to experiment right of the bat in a Forum I only just contacted, though to offer a more in-story explanation, she simply found herself bearing the Command Seals one day and had to travel to Fuyuki to get rid of them. True, she might have just stayed at home and waited for them to pass onto a more willing Master (which is what I assume happens if a Master refuses to answer the call of the Holy Grail), but it's not as if she doesn't have a reason to seek the Grail herself. If a more conventional Master is needed however, I have someone more ordinary prepared if you'd prefer.
As for Touko Travel, even if patented, couldn't she still use the technique? It's not as if she is monetizing it or doing anything harmful with it, she simply uses it as a mode of transportation due to it being more convenient than the other two modes of transportation. Admittedly, this too was just meant as a funny joke so I don't mind changing this at all. She'd simply switch over to one of the other two methods of broom travel.
Lastly, to clarify her basic magic abilities, it mostly deals with herbalism and enchantments, and even her healing is largely based on potions and ointments she creates herself. She is inept in the use of offensive spells so things such as curses are impossible for her, so her Witchcraft is essentially restricted to brewing and medicine crafting, though she still has knowledge of basic spells to help her out. These are pretty much just supplementary however.