It would be nice, if mojang add obsidian and ice stairs and slabs to Minecraft
Obsidian, maybe. but not ice for me. xD
Anyway, 1.13 is going to have slabs and stairs for all the variations of prismarine.
And Jeb has already said that in a future update there will be slabs and stairs of all player made stone blocks.
Ice stairs well be cool for a Disney's "frozen" castle, with elsa and her sister.