If Putin invades and takes Ukraine, he will have to figure out a way to hold it. There are basically two options: annexation and direct rule from Moscow; or the installation of a suitable puppet, presumably backed by opportunistic Ukrainian politicians and civil servants and some elements of the Russian military. Which would he choose?
Putin’s modus operandi has traditionally been to find the most competent thug available, give him the keys, and let him go. I don’t think that will work in Ukraine, given the size of the country and the level of opposition to the invasion. It would also be logically inconsistent to insist that Ukraine is organically part of Russia and then to give it a separate government. I think direct rule is the more likely option.