It's going to take quite a while before humanity will start to routinely build those kind of structures in space, and disguise them among the others as we could

It's going to take quite a while before humanity will start to routinely build those kind of structures in space, and disguise them among the others as we could do with satellites now. The preparations and the launch of something that has to build a 1000 km wide structure won't go unnoticed. Add to it all the time it will take to build the accelerator in relatively plain sight for anybody that has a strategic interest to monitor space for weapons.