Kaoski
...since when did genjutsu was capable of controlling an opponents chakra? You don't control the body either, you only use illusions(5 senses/ if you're talented enough sense of equilibrium could be possible, sense of time i only remember itachi using but that was mangekyo so don't know if it's possible otherwise) , you could train weapon handling and possibly make virtual opponents to fight against but that would need something like tsukuyomi
Apparently this universe is much more AU than one might imagine, since everything he wants to do with genjutsu doesn't make any sense, since in Naruto the Kurama clan was only feared because of its kekkeigenkai that allowed it to control the 5 senses of someone into genjutsu, that means feeling, so someone "normal" like Kurenai or any other ninja without a kekkeigenkai specialized in genjutsu can't do something like "virtual training", besides, if you wanted to do something like that, you could have done it something like in another fanfic that I read that the prota was focused on genjutsu where Kurenai from that fanfic had a technique left by her ancestors that was very difficult but allowed whoever mastered it to control the enemy's 5 senses. The way you implied in your story, it's as if all the genius ninjas who came before mc (including Tobirama who in my opinion is the most creative ninja in the use of ninjutsu) were very stupid for not thinking about using genjutsu to train the younger generation, it would be very simple to just take some genjutsu specialist and put a genjutsu class to train quickly. The point is that I don't disagree with the author's method for training using genjutsu, but at the very least there should be something that makes it exclusive to Kurenai.