The Kamen Rider SD OVA is less the start of something than the culmination; Kamen Rider SD comics had been going for about two-three years prior to it getting made. And there were a
lot of comics. Off the top of my head, we had:
Kamen Rider SD: Mighty Riders
Kamen Rider SD: Hurricane Legend
Kamen Rider SD: 爆走笑学校 (Which I keep reading as "Exploding Running Laughing School" :laugh
And at least one in Terebi Magazine, Terebi Kun & the now-defunct Terebi Land
Nearly all of which had started before or around the time the OVA was released in '93. The fascinating thing about the SD Rider comics is that they're all basically a different spin on the same story of the 11 Riders vs. Granshocker. Mighty Riders is goofy and features RX as the lead. Hurricane Legend is serious and focuses more on V3. The other ones all tended to shift (Terebi Land's had V3 as the main guy IIRC, and the Terebi Magazine one eventually introduced a new "Rider" called Batta-kun who made it into the other mags too.)
The first one of those is the one that most directly influenced the OVA (which combines elements from throughout the comic.) In fact the Mighty Riders comic is recognized as the "original" work on which it is based. Although I'd say the OVA is more of a refinement than a straight adaptation. They took the best stuff from the comic and brought it more down to Earth (the comic personalities of some of the Riders are... odd, to say the least.) The comic's still pretty good, but the ending is really weak, even for a silly story like this.
Hurricane Legend probably sounds cool, especially with a title like that, but trust me, that's one to avoid if you can help it. SD Riders + a serious storyline = does not compute. Especially later on. The ending is horrifically bad!
The others are all basically light fluff and I don't know it any of them have been collected and re-released like Mighty Riders and Hurrican Legend (both of which I picked up back in January.)
Why they never made any more OVAs is a mystery even I don't know the whole answer to, but my theory is that as the SD Riders' "multiverse" was already established (it basically *was* Kamen Rider in the early 90's aside from the movies), the OVA was probably made as a one-off that also could've doubled as a pilot for a TV series or further OVAs, but nothing ever came of it. Most of the SD Rider comics ended that year anyway aside from the Terebi Land one (which went on until 1997 when the magazine folded.) And the Terebi Magazine one which made it until 1999, although it became less about the SD Riders and more about Batta-kun. Who is like, the Kamen Rider EVE/MASKED RIDER GAIA thing in that he exists but nobody notices anymore. :laugh:
There's a new SD Riders comic called Card Warriors going on right now that features some newer Riders as well as old ones, but I haven't read it and haven't heard any plans for an animated adaptation.
