Twilight: "Now what's YOUR favorite superposition ?" lol could've came up more if its math. To wit, Twilight: "Oooh you have some Interesting..trigonometric properties . I hope you didn't lie about your sin . Hope our relationship would function properly" lol im bad even with math jokes and im not even sorry haha
Why have we only seen Spike/Rarity, Rarity trying to get with Prince Blueblood, and Shining Armor/Cadance in the plot? As much as I love this show to bits, why do Twi and the others have no romantic overarching subplot?
It could, yes, but given how the show has been episodic in format with little in the way of overarching plot or story besides occasional nods to earlier episodes I doubt that we'll see romantic subplots in the future unless the format begins to shift into a plot-based one. It could happen, but the chances (in my eye) aren't that great.
Always possible. However, as for romantic story arcs, I remember reading somewhere that it won't happen. Lauren Faust herself said, "Romance is the one thing that ruins most kids shows." I don't remember it exactly and I can't find the source, but it went something like that.