FEC ignitors that are built into many self-starting HPS lamps only need two leads to work, and use very few components. Could these be adapted into a standalone two lead lamp ignitor? I know that the integral ignition FEC HPS lamps have ignition antennas, is that strictly necessary or could it work with a normal antenna-less lamp?

Obviously to do this you would have to break open a self-starting lamp and assemble it's innards into a little box. Maybe someone could do that with an already dead FEC lamp.

Like superimposed ignitors, this would enable the use of pulse start lamps in probe start ballasts, but unlike superimposeds they would present their high voltage to the ballast windings, which is probably not so good for long term use with a probe start ballast.

Is this possible?

Not easily possible with a standard lamp. For the Iwasaki FEC’s they only work in conjunction with a resistor (a tungsten coil in the outer bulb) and a sidac (hidden in the base to help keep it cooler).  The stems of these lamps have a third leadwire to build the necessary circuit.  Without that it will not work.

The Sylvania design lamps do manage with a 2-wire stem and they comprise both the FEC and Sidac in the lamp cap, in parallel with the arc tube.  The voltage spikes are quickly lost with increasing distance, maybe it could work if very close to the lampholder.

@James
Ahh I see, so it has to be pretty close to the arc tube for it to work. Maybe a device that incorporates the ignitor into the fixture's socket would be better. But that seems unnecessarily complicated.

I wonder why Iwasaki didn't have their ignitors all in the lamp cap. Of course the lamps look cooler and are more identifiable when the components are visible in the envelope, but it seems like a lot of work just to have it in the envelope.

I am not certain about that, but my first thought is that the FEC ignitor sealed in the glass envelope is better protect from the environment, allowing a weaker housing?

If we can count fluorescent starters as "ignitors" (and I think we can - things designed to ignite a discharge in a lamp) and if we can count them also as "standalone", there were a few electronic starter designs actually relying onto the FEC principld to generate the striking voltage, so the answer to the question in the title would be "Yes,they were made and used"...

Functional wise taking the few components forming the ignitor circuit and placing them into a separate boxwon't be that big a problem (provided the distance limitation could be adressed).
The problem with the very simple FEC starting circuit (a resistor, sidac and the FEC itself) is, it could sometimes enter a thermal runaway mode, which means the thing becomes red hot. It comes from the tendency of many ceramics turning into conductors once heated.
Containing something that becomes red hod within somethinb that is already designed to house way bigger things that is more than red hot during normal operation, is not that difficult, as it would be to contain something that may become red hot in a separate plastic box.
Plus even when the runaway event by itself may not be directly destructive, it definitely becomes that way when occuring more often. And mainly at the lamp EOL the liklyhood of the runaway happening becomes way greater, so much it becomes very likely such simple ignitor circuit won't survive the lamp EOL. And combine that with the FEC being rather cheap to produce (compare to any more complex electronics), it kind of does not make much sense to just not design the ignitor as disposable part of the lamp assembly. Then you don't need to care whether it survives the lamp EOL, it is quite easy to utilize the manufacturing techniques that are already used to make the lamp and which make the thing safe when it goes into the runaway mode and quite important factor, the thing is inherently separated from atmospheric oxygen, so more likely to actually survive the high runaway temperatures whan it gets triggered before the lamp EOL.