Though the full extent of availability obviously until the games are in hand, we've seen many Pokemon available in it including gen 4 Pokemon lines both in the dex (Munchlax....hello) and "out" of the dexI don't know if I'm understanding the new Underground correctly, but is it basically just Gens 1 - 3 Pokémon available Underground at any time? If so, that doesn't really address the problem with the original DP dex which was nerfing its own region's Pokémon. I think there was a post on OI about the breakdown of each regional dex and DP's dex only had a woeful 75% of its dex available, due to many of the cross gen evo's being locked into post game.
That is the main problem with BDSP not sticking with Platinum's dex. The new Underground doesn't really address the core issue. This isn't even mentioning Platinum's vastly superior boss rosters.
There's a magby, as an example
Also I believe that post you're talking about is by me :V