Thank you for your quick replay.
1. Red numbers
I probably was phrasing it a bit unclear. Even if I have 11 workers and 6 free peasants the number will be red. See screenshot below. 
5. It was indeed not about the separation or emptiness of the armories but because of the routing done before building them. I did another test about it yesterday.
I do believe it makes sense to give players the option to destroy armories. For me the building placement is mainly about efficiency but a lot of players do want to build pretty castles. Replacing the armory or even separating it gives players the possibility to fine tune there castle designs.
The separation of the armories as I described it (destroy the one in the middle) was also in the original game possible, if I remember correctly.