In reality you only need to higher a single professional to manage his code base part time. I argue the amount of art, dialog, and other gameplay features that needs to be thought up take more than 50% of the work he does. The coding in this game is a lot compared to the usual RPGMAKER or Renpy games. There's a lot of systems in place, and everything sorta works together coherently. I'd argue the only other game that has this level of complexity is maybe Kingdom of Deception. But even in that game, it's a much less fluid game than this one. This is a very very well done game. Only other I can think of that has this many variables effecting gameplay and dialog is the Huntsman slave maker game.
Oni is still a very admirable developer. Compared to a majority of these patreon developer types, the work he does is excellent. The progression of the game is good, the girls are drawn to normal proportions, the Love and Obed system works well and has corresponding dialog.
If the current pace works for him, as in his Patreon is happy and he's happy with the money he's making, what will make him WANT to find another dev to work with him?
Oni, if you're reading this, I'm willing to work for free and take a look at your code base. Maybe teach you some better coding practices, or refactor some of the spaghetti you've written.