Here's the basic question:

If I "integrate" the post SP4 patches into a 4.91 SP4 client install, can I still run acu.exe and have it upgrade things properly?

The reason I ask is that the instructions for the post patches indicate that you can create an integrated install, but that they'll only be applied if you run setupnw.exe.

We run acu.exe so that we can run the unattend.txt file and deploy a bunch of other customized settings, whereas setupnw.exe ignores that and you get a default install.

Yes, I know SP5 is out, but after hearing all the bad things about it, I'm going to wait a very long time until those get resolved.