I'm not sure if that was sarcasm on your part,

but if it was, I would like to remind you that
it was Shani's idea to attract/subjugate the Queen to Zaton and arrange everything so that she and MC could entertain themselves with Merneith as they pleased.
Given the above, it seems quite logical that the time has come for Shani to assert her superiority over the Queen (for now, in a sexual-role capacity), and I think she is quite capable of. Ofc, this could be done as an option for those interested in role-playing power exchange games.
At the same time, the second option may be a more vanilla choice, in which Shani and the Queen remain roughly equal in this "love triangle". But personally, I find the idea of their (Shani and Zaton) joint domination over the "almighty" Queen incredibly exciting.