There are scripts like
George King's Windows Setup AIO Builder for 7-10 with install.wim / install.esd, and others.
Follow along if you want to try this by hand. This demo will combine multiple images, and prepare EI.cfg; it doesn't address any post-setup steps.
I assume you have working images to merge.
We're combining different Windows releases in my example, but works exactly the same for different editions of the same release.
NTLite needs a little help, install the
Windows ADK and copy \Program Files\Windows AIK\Tools\amd64\imagex.exe to an easier location. You might find random copies of imagex online, but stick to the official version.
Extract your ISO images to separate folders (7-Zip, etc).
Add "Image directory" for each distribution, but don't click on anything. Look up which images you want to merge.
Now append each of your selected images to the same WIM (pay attention to image number).
imagex.exe /export Win7_Ult_SP1_English_x64\sources\install.wim 4 merged.wim "Windows 7"
imagex.exe /export Win8.1_English_x64\sources\install.exe 1 merged.wim "Windows 8"
imagex.exe /export Win10_21H1_English_x64\sources\install.wim 6 MERGED.wim "Windows 10"
Rename this merged WIM as install.wim, and overwrite the original file in your target's sources folder. The target should be the highest numbered Windows release in your collection. The boot.wim will work with older images.
Now open the folder in NTLite. We have our imported images.
Finally, we need to create
sources\EI.cfg to select which editions are eligible for installation. We don't want Setup to automatically pick which edition for us (especially if it finds a previous installation).
[EditionID]
[Channel]
Retail
[VL]
0
Click on your folder name, export to ISO. Now you get the idea; it works for any set of random images. When you combine builds from the same release (W10 Home, Home N, Pro, Pro N, etc.) disk space is reduced by file de-duplication. This won't happen when you have different releases present (W7, 8, 10).
If disk space is no problem, combine as many images as you want. You may encounter the 4GB FAT32 hard limit on install.wim for a UEFI/Secure Boot system. Figure it out.
Post-setup customization will be challenging, you must have scripts or tools which work on every image. This is why AIO's are hard: merging images is easy, scripting & testing them is hard. Can it work? Yes. But don't be upset if people don't help you debug it.
DO NOT DISTRIBUTE AIO ISO's. Sharing will violate your license agreement.
THIS IS UNSUPPORTED, DO NOT ASK ME FOR HELP.