I would say that it is save to say that FZ will never have a simulator... In order to have a simulator, every component would have to include SPICE, where each pin is giver a value and predict circuit behavior... that means the every component and file format in FZ would need to rewritten to implement SPICE. Component manufactures do provide SPICE for their parts to be used in simulators. Every non-discrete part would require the part made for a particular manufacture and include their SPICE for that part... I don't think the average FZ user making parts for others to use could accomplish creating a part with SPICE.
There are free programs on the www that you can create simulations that have a vast number of parts in their libraries. You could always do a simulation their and recreate it in FZ...