Build an app using iBuildApp, customize later outside of iBuildApp?

I would like to build an app using iBuildApp, and I may then want to have an app custom built for me later when I have more money to invest in it.

If I have the custom-built app made, I will want to be able to have it updated on my users' phones, without requiring them to download my new, custom app separately. In other words, If I have the custom app built later, I will want to replace the iBuildApp that my users have downloaded on their phones with the custom built app, without requiring them to go download the new app separately.

Is this possible?

I was thinking that it might be possible if I can get the source code of the app that I created on iBuildApp and customize it as I see fit, then send it out as an update. Is this correct?

Thanks in advance.