Can active duty be stationed at a guard or reserve base for humanitarian reassignment?

Most Guard and Reserve units have armouries. While there are a couple of posts which are owned by states (Fort Pickett, Virginia, for example) and posts which have fell into a bit of disuse and are now primarily used for Guard/Reserve functions (Defence Supply Center Richmond, for example), the active duty personnel who are stationed on those posts are assigned to active duty units. If you don't hold an MOS which they require, you're not going to get reassigned to any of those posts, plain and simple. And you're not going to be able to switch from Active Duty to the Guard or Reserve until your contract expires, at which point, you can reenlist into the Guard or Reserve.