I write the Windows 7 ISO to flash stick using Ultra ISO trial version: On File tab Write ISO or Open DVD, on Bootable tab Write Disk Image, Format, Write.
What will be there after this operation is the seven Windows 7 install folders, which I sweep into their own folder until they are needed and then spill them into the root.
I can do the same with Vista extracted to the same pen drive, but have not tried it with different bit versions. It's worth trying, but I just use separate pen drives for now.
I can also keep all of my tools for install on the same pen drive in their folders. and it doesn't interfere with bootability once the chosen OS has its folder spilled into the root to boot for install.
It is said recently here that these flash installers cannot be used for Repairs because their boot sector will be read as Windows 7 boot, however I have never experienced this and would like to hear from others about this.