All of the things you mentioned could happen. I'm not, and I don't think OP is, at all unaware of any of that. And IF they happen, then the plan as it stands won't work - of course that's true!
But what if the complications you've listed don't actually come to pass? What if the baby eats well and sleeps well and actually OP is able to sit through lectures and change, walk, sort out the baby in the breaks with no disruption? What if she inevitably misses some parts of lectures because she is a responsible adult and removes the baby should it fuss but actually that's much easier to catch up on than missing months and months because others have deemed she should stay at home??
I could have done this plan with my first baby, but definitely not with my second, they were just very different children. - I'm sure OP is aware that this might not be feasible, she's not asking to turn the lecture theatres into a nursery, she's asking to sit quietly with a newborn and carry on with her life.
I think people are assuming OP is incapable of understanding that a crying baby needs to leave the room, I think people are assuming that babies scream from morning to night with no exceptions, I think people are hugely exaggerating how much disruption someone walking out of a lecture theatre will cause.
If a dedicated, keen woman was doing the herculean task of trying to study at the same time as caring for a newborn round the clock and in order to do that brought her baby to lectures one day a week for a few months and the baby was docile and quiet (as mine would have been) and she was clearly doing everything necessary to be considerate of other students then you'd have to be a real... 'character' to object to it simply on principle.