[@VitaVitaAR]
Yoshika is unquestioningly loyal to her master, the two are canonically pretty much inseparable, and furthermore Yoshika is treated more like an option than a separate entity during Seiga's battle in Ten Desires, so I don't really see why she should be treated differently here. Additionally, I saw another player using a supporting NPC as equipment, and you let them through with no issues at all. I assumed that meant there was a precedent. 

As for unspecified sorceries, it won't be anything gamebreaking. Just things that one can expect from a stage 4.