Deployment of MSP files

It turns out that you cannot patch network installation points directly.

Not surprising really. Why should Microsoft make software deployment manageable out-of-the-box?

Nevertheless, I found a useful article at

You can patch the network installation point directly, by using the following command:
msiexec /a < original .msi and localtion > /p < .msp file and location >.

However, you then need to redeploy the application afterwards. This can be done from within group policy.