Ok - i found the problem. The script has to run as Administrator under Windows 7 and up to actually transfer the commands to the Application windows.
Interestingly enough, this only seems to be a problem with Absolute Manage/Heat Lanrev.
Now on to getting this into the image. I was thinking about a Windows Task which deactivates itself after three days, but when run as a task, the script doesn't work anymore (even if run as "System" user).
So, I did it in the unattended.xml as a synchronos command, right after the Agent gets started and runs its SDCheck.
Deployment tools (such as LANrev) are intended to deploy things silently. The installers might not be launched in the context of the user (though you can specify that). If you need to prompt the user first, you can use the "User Interaction" tab within LANrev to allow the user to be informed first.
I know about those Options. And as I wrote, we usually let the user decide when to install Software. But in the case of an initial rollout this is cumbersome. Especcially when you need to get new Systems out fast.
And as I do not whish to change all packages to install automatically, nor do I whish to duplicate existing packages with different settings, the AutoIT solutions seems a good way to go.
Now I have it in the first run commands of my unattend.xml and all the initial Software installs just get an automatic "OK".