How about this...you tell me why any of your complaints are bad for silkworm farming. From what I have seen in the silk industry that building would be one of the best and cleanest silk farm buildings around. Most I have seen were damn near grass huts.
So why is a metal building bad for worms? Do gates not close when they have rust on a wheel?
And you forgot to mention the expense of guard towers and those think laser guided nukes for blasting the mutant worms when the start a riot and try to escape. Security must be taken seriously