I just came up with this while I was playing Omnivora in Singleplayer. I thought of the idea of a sci-fi themed fishing and plant raising RP gamemode on island maps such as rp_saari.
Anyway you could play as three different races. (Or more if you want to add custom races). The races would be Human, Alien, and Hybrids.
And the basic way to play the game is to fish for food that gives health, or seeds to make plants which can destroy NPCS and make “artifacts” which consist of weapons, or entities that you can store (like the pocket SWEP from DarkRP) in the server.
One of the things that I thought of for artifacts is stuff that can be carried around and used more then once (Like a drug lab) or that can cause an effect in a certain area (Like the Radioactive Waste in the Toolbox).
If you have more ideas to expand on this let me know.