minato if sent to kamui cannot survive for long... it was proved in kaguya arc that it takes enormous amount of chakra to stay alive in someone else's dimension... naruto's clone vanished in no time in kaguya's dimension... kakashi possessing the other eye and obito were the only ones who could survive in kamuiland for long... that's how obito was able to finish opponents by sending them to kamuiland... if they can still fight in kamuiland then what's the point of sending them there...
Like someone's already said obito had all the Intel and advantages over Minato and he still lost, Now if Minato had Intel on kamui and other stuff Obito would never have stood a chance against Minato. Obito have battle experience means nothing when it comes to Minato
Minato's Speed is faster then Obito's Kamui and could teleport there, how did sasuke and karin and sakura, and a nearly Naruto survive there, its not like Minato is just gonna wait there he would know if staying thee will be a disadvantage for him
that is if obito opens the portal... but if obito sends him there and then keeps portal closed for sometime then minato can't get out... obviously if he uses kamui again in short time then two worlds will get connected and minato can teleport out...
Minato can teleport to any place he has marked, there is no reason to believe that he can't teleport out of the dimension or that states otherwise. If he can't reverse summoning will do the trick.
for minato to teleport to a marking he needs to be able to sense that marking... he sensed his marking vanished from obito after absorbing jubi... also that's how he knows where his markings are....he uses cakra to teleport and kamui cuts off connection between two worlds thus minato needed to avoid kamui... if what you suggest was possible, minato didn't need to avoid kamui at all after knowing that it's an S/T jutsu and obito wouldn't need kaguya to open portal to travel to kaguya's dimensions...
