I see. In other setup engine, that would be resolved by running the original setup again, pretty straightforward and logical to me.
So maybe the installer could automatically delete the one in C:\Windows\Installer\ then ?
Also, why aren't you using the downloaded installer ? 208MB versus 62 MB, that's way more saving than using NTFS compression.
The problem is, every MSI setup is copying its installer in C:\Windows\Installer\, so the folder can easily take several GB of (wasted) space after some times. 208 MB is huge, in fact, it's the second biggest one on that folder on my laptop.