No real guidlines for smartplaying vs exploiting

[Nemeth]

An exploit is something that directly abuses a feature not ment to be in the game or a mistake in scripting or map making....

Your own quote, and that is exactly the state of deployable shields as of now. It is not meant to be possible to carry more than one, and recharge them at ammo box. It is, however, possible, as giving them the flag "throwing weapons" is currently the only way to actually make them work.