Marry Cait? But...why? Aside from the content that is likely planned for such marriage (I've seen people commenting on discord of a slut wife marriage where instead of "congratulate the bride" there is "fuck the bride"), that is. Feels more like something one would do while smashed in Vegas.
I have no idea if Savin has said on Discord anything about that being something the player could actually
do at some future point (cause I'm not over there) but the
idea of how a Mallachite initiate's marriage works is mentioned in the game, by Amina if you talk to her at Catte Temple. And it's basically
all the attendees fuck the couple. It's noted to specifically be for marriages between two initiates, though if one party isn't but wants it, something could probably be arranged.
As for why, hey, some people find that idea hot. I've got one Champ who would think nothing of a wedding ceremony that's basically a huge gangbang.