No or he would have use it against juubi jin obito
No need, naruto using it. Minato: "you two are the main stars (naruto|sasuke)". Minato|Tobirama = support
Naruto was better, so while naruto prepare senjutsu, minato prepare his ninjutsu. Strategically better, and faster this way, since they just ended up to combine their jutsu anyway.
Kurama avatar speed up nature energy gathering process. So minato is fine here. Problem is he'll only have tike to add senjutsu to couple attakcs, before using all of it up.
There nothing bsm naruto had, that minato not had. Senjutsu + Kurama avatar = bsm. Bm minato have both, all that needed is kurama permission.