With the little information we have so far on Vegapunk, I gather that he is capable of manipulating the devil fruit abilities of different users in scientific experiments. We've seen this with the lasers on Kuma. The image that momo sees is almost certainly Dofla. And the little we know about Dofla's fighting capability is that he can control other people's actions. Thus, it would seem to me that Vegapunk incorporated this ability into the artificial Dragon Fruit in order to control his subject.
Building on these observations, one could form many theories about the nature of Vegapunk/Doflamingo's relationship or either of their relationships to Momo. I don't want to speculate too much, but a little bit couldn't hurt . Doflamingo clearly is integrated with the highest of powers in the WG. I am of the belief that he is related to the powers that be through blood - just a vibe I pick up, obviously anyone forming a theory at this point has little evidence but I'd be happy to try and make a more specific argument if anyone is interested. Vegapunk clearly works for the WG as well, but I am not sure if I believe he is a bad person like Dofla has demonstrated himself to be.
Anyways.... the artificial fruit being a failure in the eyes of Vegapunk might mean something different than we expect. Perhaps it was a success as far as the transformation and powers go, but the side effects of using Dofla's ability presented unknown risks to the subject and Vegapunk had the good sense to scrap the project. I wonder if the fruit opens an actual line of communication between Dofla and Momo, or if it is all in Momo's head.
Either way it is brilliant. I fully expect Momonosuke to be the next SH, and I also expect the issues surrounding the side effects of his devil fruit powers to develop into a future arc - one that potentially could bring us closer to Vegapunk and Doflamingo.