I SOLVED THIS MYSELF SECONDS LATER, LEAVING IT UP FOR OTHERS.

(So I did some deductive reasoning, and figured that Yaga Minor was my only dreadnought shipyard. So I sent Kaine alone to orbit it, and boom, the option showed up haha)

So, Ardus Kaine has returned from his negotiations, but he's currently just himself, no reaper. Fair enough, so was Ysanne Isard. But unlike Isard, when I hover over any planet, even the one Kaine is in orbit above, there is no option to upgrade despite that being what his description says.

Am I missing something? It was 35000 credits (I believe) to get the Lusankya, how do I get the Reaper?