The workaround for the GRUB bug where it does not null-terminate device paths is in the 6.7 ESXi bootloader, so I think chaining from GRUB to our bootloader will work for disk and ISO image boots now.
However, as explained earlier in this thread, the reason that chaining from GRUB into VMware's bootloader during PXE boot does not work is a limitation in GRUB. GRUB calls Stop on the UEFI PXE prototol before handing off to our bootloader, so our bootloader cannot load any more files over the network. It's not possible to restart the protocol (I tried). I don't know of a way to work around this on our side. You could perhaps try modifying GRUB to not do that.
More simply, I suggest using something other than GRUB to create menus, also as discussed earlier in this thread.
