The simple answer to the question above is Yes, and No.
Yes, you can change WinPE, and no, the changes are not supported. Obviously, if you have issues with the changes, you'll need to try removing everything, going with the default we provide, and see if the problems persist. The only support provided by Symantec for this is that we do support the inclusion of the files in the OEM folders. We do not support any custom changes you make.
Understanding how we build the preboot WIM is important - we use the WAIK folders as a source location, copy those to a temp location, overlay our own changes to this temp location, and then compress. The rest of process is how to modify the information that is overlaid into the WAIK prior to compression. By the way, this is the same process that our vendors use, thus the "OEM" folder name.
No, no such method exists for Linux Preboot.
First, find the appropriate "overlay" folders.
The BAT file in the BASE folder is what you modify to launch any application you want run at startup. For example, BGInfo, or a menu.
The "Program Files" folder is normally where you would add applications, by folder, that will need to be compiled into the product.
The Windows folder is for any changes you may need to make or add to the system folders, such as fonts, or in some cases, adding system DLL's for expanding windows PE functionality (e.g. adding DAO support).
Once all changes you desire have been made, a rebuild of the WinPE environment must be triggered.
After BootWiz completes on the server (or site server), you should be able to test the new build of the environment and see your modifications in place.
For my personal WinPE, I have added some things I like to have for troubleshooting. You may want to add things for your environment, such as a custom graphic / background, or whatever. Here is what I found and have done: (Note: for all of my tools, to save space in WinPE and speed in the download of the automation environment, I pull anything out of my free apps that I don't absolutely need. This takes a bit more time but is worth-it in the long run.)(Note2: None of these applications can be posted by Symantec unless OWNED by Symantec for legal reasons, so you'll have to go find them yourself.
For instance, I have experimented with three "free" or "open source" utilities, one called RocketDock, a menu that will run in PE, and another called BGInfo, which modifies the background to display key pieces of information, and yet another called A43 which is a file-manager-like tool that will run, not fully functional, but at least run in PE. Each app I simply create a folder for and drop into Program Files. Then I modified the BAT file in the BASE folder to run one or two of them automatically.
There is no interface in the console for these changes! Remember that.
Replicating custom WIM files is NOT supported! Neither is replicating a WIM file we build. It is a known issue that each WIM must be built on each Site Server for proper functionality.
Adding too much to the WIM will cause problems. We have a fixed memory size we allocate for storing the WIM in RAM of 512M, so if the WIM, or the functions you call, exceed the memory allocated and/or space allocated, there will be problems.