Arent their abilities kind of overlapping at this point? I mean, what happens if Kaguya, Sanae, Tenshi and Reimilia are on one table?
We haven't really seen Remilia in action yet so no clue on what she does but the other three are actually fairly different. Sanae's ability gives her a tenhou/chiihou whenever she starts losing, which we already saw Youmu get around by sending her into the negatives in one shot.
Tenshi's ability is actually a bit trickier, since it isn't that she's getting tenhou because of the blessing of a god or something like that. If we take what she said at face value she is stacking the wall and rigging the dice throw not through classic cheating like Marisa but through supernatural means. Essentially it's Marisa's strategy except she can't be directly stopped, can alter all walls instead of just the one in front of her, and on top of that she probably doesn't have the limiter of "needing to be losing". If I had to guess the way around it is for Marisa to mess with the wall after it's already been stacked by Tenshi, but that'll be impossible without Sekibanki's cooperation and even then a couple things would have to line up (such as Tenshi going for a double riichi instead of just getting tenhou again, which I think we can assume she did out of hubris?). Either way we'll probably find out more in the next chapter.
As for what'd happen if those 4 played in the same table, unless Remilia's ability overruled it, I would say Kaguya wins. As long as her ability is in effect there's no escaping a tie. Marisa had to basically hold her hostage by breaking the rules in order to force her to disable it, so unless the other three tried the same the princess would have the win on the bag. Or not. Maybe they'd just keep playing forever.
I dont think Sanae needed to lose, since apparently winning by getting the best outcome over and over again would definitely put you out of danger zone. But yes, she had a cooldown.
In hindsight, Tenshis ability is really underwhelming if you consider the fact that Marisa could do the same but without any restriction, only overruled by supernatural abilities. And since Tenshi physically does something, she would automatically lose against "reality changing" abilities such as Kaguya and Sanae, at least former proved to change the tiles Marisa cheated with.
