Is it possible for me to add mannequins through the console in some way or form? Or is there a mod that lets me place and buy them?
Short answer: Wait for a mod.
Long answer: You can sort of wing it with with the console.
SAVE BEFORE YOU DO THIS IN CASE YOU DON'T LIKE THE RESULTS.
This creates a living mannequin NPC at your location. Did you know mannequins are actually NPCs with disabled animations? Creepy. Unfortunately, there is no way to attach the special script that mannequins have to the NPC you just created using the console. However:
First, open the console, click on the mannequin so that it's ID is shown:
Note that since the mannequin lacks whatever mannequin script the real implementations use you will have to use
You do this at your own risk, as we have no idea what kind of black magic the mannequin script contains to protect your items, make the weapons display, etc. The console is really for debugging the game, not editing the game.