Replacing GuiXT files in a SAP GUI patch: We are deploying a new SAP GUI patch level and would like to deploy a particular version of GuiXT with it. Is this possible?

Yes, you may replace guixt.exe and guixt.dll in the SAP GUI patch level. In the SAP guide "NetWeaver SAPSetup" (also called "NW SAPSetup") there is a chapter 'Adding New SAP Front-End Components to an existing Installation Server' describing the procedure.

We cite the relevant part; please see SAP documentation for more details:

"The installation server can be updated with new SAP Components using one of the following two methods:

(1) Using NWUpdateInstServer.exe

Start NWUpdateInstServer.exe from the SETUP directory of the CD / Source containing the component to be added
Supply the path of the installation server and follow the wizard to update it with components available on the source.
When using NWUpdateInstServer, the steps to be followed are quite similar to what was seen between Steps 4 and 7 of Installation Server Creation.

(2) Using NWSAPSetupAdmin.exe

Start NWSAPSetupAdmin.exe from the SETUP directory of the Installation Server that needs to be updated with the new component.
Click on the toolbar button that states “Import Products”
Follow the wizard and supply the path to source where the Product to be inserted into the Installation Server is available."