As a matter of fact, I am currently in the process of planning out a first-person shooter rpg set in a sci-fi universe. Ever play Borderlands? I’ll be shooting for something similar. Working out the specifics of procedural weapon generation, which is what gave Borderlands its 6 million plus weapons. Now I won’t actually start on this until at least the first alpha version is finished on my current project, so you’ve got a head start.
Anyway, absolutely anything is possible in blender. But with that said, making a shooter is a bit more difficult than modeling guns and setting parents, especially if there are rpg elements involved. My advice: plan your game out, and make sure you know what you’re doing before you get frustrated and starting posting “Urgent HELP plzzzz!!!” all over the internet. Good luck!
Oh, and if you aren’t proficient in python, I suggest reading up before tackling some of the rpg stuff.