Hi, so I came up with this bug where Dream ball starters (the ones available: Kanto, Hoenn and Sinnoh) and porygon are marked as illegal
with the new breeding mechanics they should be possible, here's a source a source showing where can those be obtained http://www.serebii.net/blackwhite/dreamworldpokemon.shtml
and helpful doc to check legality https://docs.google.com/spreadsheets/d/1UiHRaJ6LkAz-57QWptiCKMnwbUu8GLeftjiNGI4K67A/edit#gid=0
255 - Torchic - 67433B9C00D4.pk7
007 - Squirtle - 3BB2CF8F4518.pk7