Gema showed a few of Jigglypuff's custom moves.
Sing 2: Gives it three different hitboxes! The last hit KO'd Peach at 120% or so.
Sing 3: Gives it reflector properties like Mario's Cape, but also very slow. Because of the slow speed, it might not be useful, UNLESS Jigglypuff can cancel Sing by touching the ledge like in Brawl, then it'd be very useful.
Rest 2: Jigglypuff jumps upwards like Sonic, but falls asleep at the peak. This acts as her 3rd jump. HOWEVER, it doesn't sweetspot edges, so it's probably a bit useless. At the cost of the height, the power is reduced to Brawl's Rest.
Also, Jigglypuff still KOs herself if her shield breaks.