You can use \_ISO\Switch_E2B.exe to switch in any .imgPTN file.
I totally agree that it is inconvenient!
However, the reason it is done this way is:
1. Some UEFI BIOSes have a very annoying bug. If a valid UEFI boot file is present, these BIOSes will NEVER MBR-boot from the USB drive. So if you want to boot to Hirens say in MBR mode (or just the E2B menu), you cannot do that (even if CSM mode is enabled in the BIOS settings).
2. FAT32 would be required which means large files >4GB could not be added.
3. grub4dos does not boot via UEFI
4. It makes adding/configuring/deleting UEFI payloads very complex.
5. You would have to use an application to add/delete UEFI payloads and that app would need to 'know' about all possible payloads and be maintained monthly and ongoing.
6. Secure boot would be compromised
If you just want a Windows payload multiboot USB drive, take a look at WinSetupFromUSB. This does support MBR+UEFI, but if you are using it on lots of different systems, snag #1 above may catch you out!
Subject Re: Easy2Boot on UEFI system