It depends where you will be diving in the Maldives, but in any case, the boat traffic can't be compared to Egypt for example, even if in some places, it can be intense.
Of course, the SMB is there to signal divers to other boat, but also to signal yourself to your boat. As currents can be strong, you can drift pretty far, pretty quickly, especially if you are diving a channel with an outgoing current.
Being outside an atoll drifting in the Indian Ocean with a strong outgoing current, without a SMB is not a good idea (even with a SMB in some case... sometimes, the swell is bigger than the boat, thus the boat can't see you, even with a SMB. Better to not drift to far outside at any time.)
In any case, I believe it's better to have a reel and to inflate the SMB at the safety stop. Your boat will start to move towards you, and with a good captain, even protect you from other boat if needed.
Enjoy you holidays, I've heard the MV Orion is very good!