It looks good as a concept, you're essentially thinking Nosferatu but combined with Sing?
That said I have a couple points:
- One could just fuse the two moves really and have Dream Eater be a follow up. Sure, would be potentially janky, but would free up a precious Special move slot for something else, which may not be accurate to Pokemon but would give more needed versatility.
- Jigglypuff's potential reward off of Sing is extremely high - not just Rest, but also F-Smash and other attacks. It's partly why it's damn hard to land generally. While Gengar (or any other Hypnosis user) could have similarily high reward - see Nosferatu - it's worth noting that Nosferatu also has a -esque 3 max uses before the tome is discarded, with 30 seconds cooldown on the move after discardment.
Also, worth noting that Nosferatu is really difficult to land and far from as safe as say
's Chomp. It's
active on Frames 15-18 (1/4 of a second), with the endlag lasting until frame 49 - half a second:
(And yes, the blue is invurnerability.)
While Sing's three pulses come
at frames 27-36, 61-70 and 100-115 respectively - it ends on frame 149, illustrating how much of a commitment Sing is:
Hypnosis + Dream Eater could work along those lines... and hey, there's some precedent with Pokemon's PP system.