@User: I don't know if you can do something like this, but I have xcircuit set up so that every output line to be generated in the netlist is prefixed by a tag; when you go do make a netlist, you'll get a choice of what netlist you want to write from the set of tags found in the design. So I could do

ngspice:<something ngspice-specific>

but also

xyce:<something xyce-specific>

, and then when I go to create the netlist I'll get a menu selection of

Write ngspice

and

Write xyce

, and the netlist will be compatible with the simulator of choice.