The equals stuff doesn't work quite well. Kishi portrays Team 7 as equals too, so, for Sakura to get SM Sasuke would have to acquire it as well.
And Oro can't use senjutsu. This makes sense to me, senjutsu is only for Jiraiya and Naruto, it doesn't have to do with equals.
Tsunade couldn't possibly have held back, she knew who she was going up against, all the kages knew, hence why they fought 5v1. In the beggining Madara didn't even retaliated and he never went all out during the whole battle, she could have stepped aside and gather senjutsu. Madara his so arrogant that he would let her gather strenght to make the combat more enjoyable, i'm sure.
And what's the purpose of senjutsu? To enhance the power of one's jutsus. So technically, she would heal the others and herself much better, she would punch much harder, she would gain a speed boost, sensory abilities and Kishi knows what else.
Against Pain she was too tired and he isn't arrogant like Madara.