This client-side addon for Armor Poser mod enables players to possess an Armor Stand.
First of all, press SHIFT+R to enter the "Limbo" state (become ghost). You basically get a worse version of freecam with cool shaders. Then, to possess an armor stand, hover your cursor over it and press R. To leave the chosen armor stand's body just press SHIFT+R again. To return to your original body you'll have to manually fly over and use R on youself.
So, again,
SHIFT + R - become ghost
R - enter the body
You can reconfigure "R" to any other preferrable key.
While inside the Armor Stand, by pressing "Open Inventory" key you will open this Armor Stand's config menu. You can modify it on the fly! You can also enable walking animation by pressing respective button in the menu.
There are a lot of known bugs and issues, sorry about that :(
This addon was created for a YouTube video and then published under the MIT License. Don't expect a lot of updates, code is opensource and free to expand on!