I might work on this game sometime again (no promise though)*.
So now would be a good time if anyone knows any bugs or tricks that haven't been reported yet.
I found that the Japanese version Nekketsu Koukou Dodgeball-bu Soccer-hen is basicly a v1.0 to this game and is glitch-heavier. Nintendo World Cup is a v1.1, you could say. Not sure if they changed much in the EU release. And Kunio's Nekketsu Soccer League is v2.0 :)
I found a few things in the J Soccer-hen game that could find a use in a playaround or "password to last match" TAS, but I'd rather not spoil them here. If someone really is interested, PM me.
From what I remember back in the day when I watched youtube videos, there was a bug that made it possible to walk around behind the goal, out of bounds. But I can't find the vid (maybe it's gone) and I'm not able to do it.