The diode on the mosfet does a couple of things, both of them good. It takes care of ESD and it acts as an inductive load clamp. It does a much better job than other approaches. The diode costs a cent to a few cents. The resistor costs a fraction of a cent. Either way it's not a cost driver in the design.
If the relay is powering up your stepper drivers, then a 1 A relay isn't going to be enough. The diode across the relay is to protect the transistor. As soon as somebody decides to attach a relay to one of your mosfets, you get the same sort of spike / same problem / same solution. Even a "resistive" heater may be quite inductive at the speed the feet's may be switching.
If the relay is powering up your stepper drivers, then a 1 A relay isn't going to be enough. The diode across the relay is to protect the transistor. As soon as somebody decides to attach a relay to one of your mosfets, you get the same sort of spike / same problem / same solution. Even a "resistive" heater may be quite inductive at the speed the feet's may be switching.