I write the Windows 7 installer to stick using UltraISO Software To Create Bootable USB Flash Drive.
When it completes you'll notice that the installer's folders are in the stick root, where they can co-exist with other tools and program apps, as I've done for years with a 16gb Kingston Data Traveler.
To boot another bit version or Vista/Win8, you only need to put the extant installer folders away in their own storage folder and extract the desired installer folders into the stick - which is already permanent bootsected by UltraISO to boot an nt60 installer until it is wiped with Diskpart Clean Command
Keep each OS/Bit version installer folders in a separate folder on or off the stick.
This lacks the boot menu so is a manual method but it's always worked so well for me that I haven't gone looking for anything more which requires a boot loader.
If you only need the Repair disk ISO's those can be written to stick using Win2Flash.