SakuyaA was my first to clear extra with. Curving electric bullets brought back memories of Iku...but Raiko doesn't overdo curving lasers, thankfully. For the first spell with these lasers, if you dodge the first wave of lasers, you tend to dodge the second set without moving much, given you are towards the bottom of the screen. Just be wary of the eye-bleeding Miko bullets. The second card with the lasers requires some foresight, since the lasers increase in number per wave. It is really easy to overlook a laser or two in the later stages of the attack, and the blinding bullets don't help. Just be extra careful dealing with those, since you can practice them all day, but in a real run, you are many times more likely to make a mistake.
Can't say I'd be too thrilled on another Phantasmagoria. I barely played the other two. But wouldn't the pattern be 3>9>18? It took the third game for the first one to come out, then 6 more for the next, so 9 for the next one. Like how Marisa was a stage 4 boss for 2>4>8>(theoretically) 16. Mathematical patterns aside, I think it is probably best to wait and see what ZUN has planned, (or is going to plan) otherwise these sequences are going to have us waiting forever for another "x" game.