Best way to export XPS project to ISE?

I have a design that was built with XPS 8.2.03. I want to lock down everything in the design except one custom OPB peripheral I created. I want other users to be able to modify that peripheral (from user_logic.vhd down) and recompile the design with only the ISE software.

If I use "export to ISE" are they still able to modify user_logic.vhd and below? Do they still need an XPS install to build? Does ISE allow them to initialize the BRAMs with my bootloader .elf?

Maybe somebody in this group has already done this? I want users to be able to implement some custom hardware on my product but I don't want them messing with the CPU and other peripherals and I'm trying to avoid the expense of forcing them to buy XPS since they don't really need it.

Thanks, Clark