"Rather than input the Section 1231 gain on the K-1 input one could move the gain to the 4797 input using the disposition screen and title the gain as "K-1 Passthrough ABC LLC", which would trigger the 25% deduction."

... that looks like a pretty simple workaround to me? I've done much worse to get an accurate return that meets e-file specs. Don't forget to manually adjust your basis in the K-1 input screen.