Is there a ideal amount of updates you should push per branch?

I am about to work on a rebuild of my app. However there are currently users using the live app so I will have to do the entire rebuild and then push it live at once. In the past is was much easier to do so with a separate dev environment and when you were done you would just push the other environment.

Now it appears you can only push the main version live and you will need to sync the changes of the branch with the main app. I am concerned that the large amount of changes I am about to make will effect this sync.

Has anyone encountered this before? Or are there any tips on how to do a rebuild using the branches?

Be sure to read this:

Thanks! I will definitely take a look at this.