Given the small number of topics, it would seem easier to
have one project provided you can get the layouts you need.
The problem is that the CPD for the all in one project has to
know about all the topics and to do that, you have to import them.
There aren't many and you can import all the topics in a folder in
one go so it shouldn't take that long.
Your cross project links will be broken so you'll have an
exercise on fixing that.
The map files can probably be manually merged in Notepad or
similar. Similarly with the TOC and Index files.
Take a copy of the project and run some tests. It will need
some tweaking. Only you can decide whether it is worth the effort.
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