some mods are only needed server side, others are needed client side only. Simply being able to separate them if one desired would help for whatever their reasons may be. Like the reason i have that led to my inquiry. I am developing a modpack update, which has a public server with an existing world. Have come into situations where i may remove some mods from the pack, in turn gotta test for the public server.(making sure world can adept the changes, etc). The server is running with SpongeForge with plugins. These dont go to the client, being able to separate these in the server directory would make it easier to change forge only mods/files. I'm probably bad at organization. Wasn't suggesting this be added, the question was more on the side of "is this possible".
But hey, having the option to choose this layout isn't the worst idea/question i've seen in posts.
From the reply i think i can deduce the answer is no. So thanks anyway.