Best Guess: I wonder if those MUI-setups are Multilingual User Interface setups. I think you should get on a virtual machine and try to run the setup.exe
instead (if there is one) and then go to "Custom" or equivalent to see if you get a feature selection dialog. Then you should select Word and Excel to install fully and you can disable most other features (don't disable the shared features, just the other apps would be my suggestion - Outlook, PowerPoint, etc...). It is possible that those MSI files you mention can be used directly. You could try to run them - but only on a virtual of course. Or on a computer which does not matter - test computer of some sort. Look for a custom option and a feature dialog there too. Sorry, all I can suggest without installation media access.
Sure?: With all that said, Office on a domain server? Do you mean domain controller? (hope not). Sounds like a very dangerous move if you ask me - with all the security holes Office contains. At least make sure to run Windows Update or Office Update or whatever mechanism you have to deploy security fixes. Can I be curious and ask why the server needs Office? Is it for automation only?
Viewer for MSI Files: You can open and inspect MSI files using the free tools Orca, SuperOrca or InstEd (links towards bottom). I have an old answer on superuser showing how MSI features can be seen inside the MSI file.