I think bike lockers are a good solution here. My first thought was some kind of shed or other dedicated building, but that isn't portable (except for more or less demolition and reconstruction). Lockers fulfill your other requirements pretty well, and it would be possible to move them if needed.

The question of exactly how much security you need is very locale-dependent. Do you need to protect against someone wielding angle grinders and bolt cutters, or just someone walking down the street and performing an opportunistic theft? Also, if you do go for a shared option where all ten bikes are under one roof, you should consider the trustworthiness of your fellow residents. You also may need to be more careful about your relationship with the residents in that situation--you wouldn't want to piss a neighbor off (regardless of whose fault) and have them damage or steal your bike as a result.

I think bike lockers are a good solution here. My first thought was some kind of shed or other dedicated building, but that isn't portable (except for more or less demolition and reconstruction). Lockers fulfill your other requirements pretty well, and it would be possible to move them if needed.

The question of exactly how much security you need is very locale-dependent. Do you need to protect against someone executing a planned heist wielding angle grinders and bolt cutters, or just someone walking down the street and performing an opportunistic theft? Also, if you do go for a shared option where all ten bikes are under one roof, you should consider the trustworthiness of your fellow residents. You also may need to be more careful about your relationship with the residents in that situation--you wouldn't want to piss a neighbor off (regardless of whose fault) and have them damage or steal your bike as a result.