I always do that, worry not. Nasty errors happen when I dont. I normally add something like _(name)_edit to the MDL when i do so.
Thank you!

Yeah you're right on that. But that's if and only if they are not modified what-so-ever. Also the original content may be modified and then there will be a conflict. Since for knee deep I'm never going to touch the assets again, you can use them if you don't modify them, or if you do modify them make sure to change file paths for models and materials.

Two maps can have the same custom content as long as the new map does not modify the content. If the MDLs, VMTs and VTFs remain the same, there should be no problems, as far as I know.
Now, do you consent to me using the rocks from your kneedeep map? I quite like them. (Plus other props that may come from the decompilement)

Sometimes, usually if they ask me and they are segregating the file systems so they do not corrupt eachother if people have both addons subbed, that's my main concern.

Do you allow people to use assets from your maps for their maps?

Where do I find any info about your upcoming Ruin type game, Is there like a discord server or something?