castle siege IMO is easily a counterpick.
Hanenbow I don't have the energy to argue against right now, but if you leave it on, expect me and anyone else who wants to win the tournament to be EXTREMELY GAY on that stage. srsly it's not even fun winning on that stage.
Also, I don't think Lylat and PS1 are good neutral stages.
Lylat - you may say "Well the stage tilts for everyone so it ends up being neutral".
But here's the deal with that stage. Choose metaknight and try to walk off the edge for an edgehog. Eazy peezy lemon squeezy right? Now try it with Marth... No? Diddy? No? There are a bunch of characters who have trouble grabbing the edge on this stage. It's clearly a good counterpick against those characters showing good knowledge of character-stage weaknesses.
PS1 - You may say "Well, the lip affects everybody's recovery and the Windmill is gay to everyone".
So here's whats up with that stage. The lip way more greatly hinders people with certain recoveries. I'm not going to do all the research here but I'll give some examples:
Wolf's side + b becomes way harder to do.
Wolf/Fox/Falco will have a harder time up+b'ing straight up to the ledge.
Sheik/Zelda have a harder time up+b'ing diagonally to sweetspot.
Not only that, but the lip favours other characters as well as hurting the previously mentioned characters. Examples:
Kirby: Get stuck at the lip on your up+b? No worries, just DI towards it.
Bowser: Same
DK: Same
Also, the windmill is a bit more minor but it favours smaller characters who can more easily pass through it. It also gives good opportunities for characters like P.Trainer and Zelda to safely transform.