Track multiple instances of real-world cuboid and replicate them in Unity scene

Hi guys.

Let me start by saying I am new to vuforia and unity. I want to create an PC app where the user would stack lego-like blocks to produce some sort of ondulating wall --something like this but with much smaller blocks (the blocks would be painted with an AR tracker. Also ignore the robot). I would like Vuforia to recognize each block that is placed as it is being placed in the real world, and have Unity create a corresponding virtual block in the scene. The setup could be something like this (PC instead of iPad, since I don't have access to a macbook). 

Required:

• A block appears in the unity scene when the real-world block is placed
• Blocks can be added on top of each other

Not required:

• Blocks update in unity when they are moved in real-world (although it would be fantastic). 
• That blocks can be place behind others (although I could have a turntable if that helped)

I just started, and my approach has been creating a cuboid tracker, applying it on the blocks, and placing them in the real-world. However, it seems unity can only detect one at a time. Also, are there any advantages/disadvantages in using multi-trackers vs object recognition? Finally, does this project seem feasible at all? I want this to be a proof of concept, so if I am able to aggregate ~20 blocks I am satisfied. 

Any ideas about how I can achieve this are welcome! Thank you!