Principally because I realised Multiverse supported planeswalker tokens and wondered if there was any sensible way to use that. I guess not, but it was still fun. They look all right, though.

The Design Challenge on one-drop planeswalkers suggested some abilities that might be sensible for planeswalker tokens.

I think they would need a Planeswalkertype, as they all would have the same type they would leave the battlefield as a state based effect.

No. In fact, they need to have no planeswalker type. Otherwise they would all leave the battlefield as a SBE. But in the same way that multiple morphs can coexist with Leyline of Singularity out, multiple planeswalkers with no type can coexist, because of the way the legend and planeswalker uniqueness rules are written.

This was one of the more iconic of my cards in the Bring Your Own draft yesterday. People said it was overpowered, but I'm still not convinced. If you're using it to burn face, then it's not much more effective than Exuberant Firestoker or Gruul Guildmage or Quenchable Fire, none of which were very good, or Obelisk of Alara's red ability, which is a great card but definitely not mainly due to the red ability. And if you're using them to burn creatures, it's like Jagged Lightning split across two turns.