I think it's right to somehow manage their expectations. Usually when they ask for something that is very far away from what the Maker is supposed to be, chances are they chose the wrong one and others would work better. If they still want to do it, they should know that it is not within the Maker, could potentially be added by scripts or plugins, but is a huge undertaking.
Someone that asks for MMO stuff should know, that it is nearly impossible and nobody ever managed to do it properly. Saying "nobody did it so far but if you REALLY try hard you will be the first"... would in my opinion be worse than "it's impossible".