Hey Arcanum,
Ian is correct, when I originally read this post, I somehow missed that the paths where you were altering the bootstrap files are in fact the paths for a 32-Bit WinPE environment. For whatever reason, it seems the folks at Symantec decided that GSS would not consider 32-Bit UEFI systems to be a valid or proper configurations and at this time, GSS does not support 32-Bit UEFI systems. If you are in fact trying to service a system that is 32-Bit UEFI only, GSS will not work for you. As Ian already mentioned 64-Bit UEFI is considered proper by GSS and will work without issue. There are some configurations that might cause you some grief and just in case you hadn't already encountered these yourself, some things that could prevent this from working for you are listed below:
1. The WinPE environment you are using to attempt to boot UEFI systems must be of 64-Bit Architecture and must be at least WinPE 4.0 or higher.
Reason: Older WinPEs such as 3.0/3.1 to my knowledge are legacy only and will not allow you to service UEFI systems natively.
2. In the Altiris Console, open the PXE Configuration Utility and go to the Multicast Tab. Uncheck the first box from the top "Enable MTFTP."
Reason: A few years back we received some devices with newer Intel Chipsets and these devices would not respond to the Altiris server if this value was enabled.
3. If you are attempting to test this on UEFI Virtual Machines, you must disable Secure Boot to get the GSS server to respond to the Virtual Machines. In my experience this is true of Hyper-V as well as VMWare. I have not tested Virtual Box, but I suspect the same is true.
Reason: Again im not sure why but GSS only responds to UEFI VMs if Secure Boot is turned off in the virtual firmware.
The sad part about how GSS selectively services UEFI Systems is that Microsoft does not suffer from the same limitations. A Windows Server running Windows Deployment Services will respond to, and fully service 32-Bit or 64-Bit UEFI Systems. WDS also does not require you to disable Secure Boot to get a response from the server and I hope that GSS figures out how to implement this soon because frankly its frustrating.
If you want to confirm UEFI functionality on systems you suspect are 32-Bit only, I encourage you to spin up a wds server and add boot media to it. This would also allow you to service such devices in the interim while GSS plays catch up.
PS: For examples of 32-Bit UEFI only systems, here are just a few we have had to deal with in the past.
HP Elitepad 900
HP ProTab 480
HP Stream 7
Acer Iconia W4
Acer Iconia W1-810
Here are also some 64-Bit UEFI only systems:
All Surface Pros (Non-RT)
HP Elitepad 1000
HP Stream 11
Hopefully this helps you out some, If this happens to solve your issue, kindly mark it as a solution. Good Luck! :)