Pros:

-Creative
-Interesting
-Design 

Cons:

-End boss is confusing and common "Oh hey look a charger" got old fast
-Easy witches due to being able to shot though glass.
-Solo is fun (No deduction as you said CO-OP)

Conclusion:

-May be fun if you have nothing better to do or cant find any other maps

Pros:

-Makes the Chrome shotgun Chrome

Cons:

-VAVLe might jealous that you made Chrome, chrome and not grey (I blame gaben)

Conclusion:

Why isn't it mandatory