Add another dev, and if they are aligned, they can knock it out of the park.
Add another dev? Better have a damn good reason.
I forgot how productive a single person can be until I joined my recent company. I'm the only dev working on a sizeable application. I have all the resources I need and zero distractions. I can't believe how smooth progress is and I whince at what would happen if we added other team members without having a clear role for each person and a pressing need for them. Stand-ups are devastating to productivity.
I just left a number of huge enterprises. I could barely get anything done at any of them. Sizeable teams that could barely push out a web app. Its no wonder they have to acquire companies that were built by three devs to innovate.