Sorry... I gave you negative feedback while you gave me positive feedback....
The Up B you mentioned (Bounce) seems a lot like DeDeDe's Up B, and with DeDeDe being a heavyweight, I struggle to imagine how this would work well for Hoppip seeing how it's incredibly light. Snakes Up B seems to be more fitting, where he begins to rise and rise and rise. (Fly/Updraft/Float.... not sure what you could call it)
Down B moves normally are used for Transformation, Counters, or Area Attacks. Perhaps this is where you could have Hoppip to charge up for Solar Beam..? (Making it only possibly to do when "rooted" into the ground (AKA Just on the ground, not in the air)
If Down B were to be Solar Beams charge, then either Side B or Neutral B could be the Solar Beam itself (Functioning similarly to ROB's laser)
Which ever special you have left could be Stun Spore. Like you said, it could freeze/slow down the opponant (Maybe even give them those flowers on their heads?) The attack would be weaker, but have more effect. It's range could be similar to where Metaknights cape goes for his final smash.... know what I mean?
I hope that's given you a bit of a better understand for what I PERSONALLY imagine for Hoppips special attacks. Yet again, it's your project, but I look forward to trying it out no matter which way you go. (Feel free to spit out ideas for Dugtrio
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