Routing Matrix with a large number of I/O
I would use a port expander that uses I2C for communications. One example is the PCA9555. You can add up to eight by setting the address bits (A0-A2). This will give you up to 64 outputs to control the selection bits of the 4051s.



While this is all intelectionally possible, from a logic perspective, I have concerns about how this can be practically implemented. I think you need to go into more detail on what you plan to do. What the purpose is. 

Also, there are larger chip for do analog matrix switching. AD75019 is one example. https://www.analog.com/en/products/ad75019.html

They are more expensive but cost should not be the primary factor. Getting a design to work is more important. 

Do a search for "Crosspoint Switch Array" for more chips like this.