I mean sure he's planning to "seize all of Ukraine", but I don't think he wanted to make Ukraine a federal subject, at least originally. My theory was always that he wanted to capture Ukraine to force a very favourable (for him) peace agreement, install a loyal regime, keep Crimea, give independence to the Lugansk and Donetsk republics, with borders corresponding to the oblasts, and then leave. Possibly make the republics federal subjects of Russia.

The statehood threat actually strengthens my belief, it sounds like he will only annihilate Ukraine unless they give up soon. If he was planning to do that anyway, the threat makes less sense.

But of course I'm just guessing.