| It can definitely not be as simple as the series incandescent filament in the SBMV.
Closest to that was the mentionned GEs WattMiser: There the ballasting filament was complemented by the "electronic" (well, just a bunch of diodes, capacitors and resistors, plus something like sidac or thyristor diac and few passives, plus a hv pulse transformer), that part was supplying the arc by a small current during the time when the mains voltage sinewave is below the arc voltage so can not feed the arc, to maintain the ionization and so eliminate the need for the reignition spike voltage. Drawback was, it needed DC arctube, which is a bit of use complication (limits operation position).
Later (post 2000) the major makers were offering low wattage PAR CMHs (20 and maybe 35W, definitely not higher) with the complete electronic LFAC ballast in their base, for high end retail market.
The common thing of all these was the high cost of the electronic integrated ballast. That means although it would be technically possible, theat electronic ballasted selfballasted format was never used (maybe except some experiments) with anything else than the highest color quality MHs, where at least some potential customers were willing to pay the cost. Because HPS was the choice where the most important crireria is to get the cheapest light possible, there is no way anyone in that business would be ever willing to pay the extra cost of the selfballasted format.
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