Add files to existing NSIS exe?

We are currently using MSI for our product installation, but we have been considering a move to Nullsoft (which we already use for a few other things). We have a feature where our product can create a new installer with some custom settings to be distributed to users. To accomplish this with the MSI, we programmatically stream some files into an existing MSI. Can anyone tell me if there would be any way to insert files into an existing NSIS .exe?

Thanks,
Dave

Edit the existing nsis script (nsi) add what new files you need to add and recompile the nsi.
That's easy and straight forward.

This needs to be done on a client machine, which will not have a Nullsoft compiler on it.

There isn't way yet to allow add files into an existing compiled installer.

You can use this: