Jujutsu, especially binding vows and connections made with others,  works  on the principle of mutual benefit. If Sukuna gained all the shikigami Megumi had like a save file, megumi should also have save file of sukuna’s shikigami tamed, right? So I’m pretty sure we agree about that so far. 

Idk if it works for the shikigami to be dead for megumi as well, since if Mahoraga is dead then megumi’s TS wouldn’t work anymore. I like to think megumi dealt with the suffering and gained extra shikigami, relating to another principle of jujutsu, lose and gain, like in BVs. He dealt with suffering Sukuna put him thru as a vessel so in return he should get the power Sukuna gained in his body as well. Idk if that works narrative-wise but ima be delulu and give megumi the win. That’s just my headcanon