This mod is really cool! I am surely going to try it out (even though I haven't played Metroid games at all)!
I'm actually just past Wall of Flesh, and can say that the ghost at least starts selling the Arm Cannons and Power Suit.Chozo Ghost Npc - I like the idea and design of this npc but what it sells simply lacks, all he sells is a single boss spawner which will quickly make this npc obsolete unless you need extra ores from the boss. I'm sure there will be more items to be sold from this npc in the future but for now it's quite stale.
There's at least more Metroid hatches than the blue ones (green, yellow and red specifically), if that's what you meant. There's also Crumble Blocks and Grip Ledges, though I haven't actually done anything with them yet.Adventure Maps - It's no surprise that people are going to want to make adventure maps using this mod and I'm one of those people. If you were able to craft bomb blocks, speed booster blocks, screw attack blocks, maybe even beam doors and most things that are in the metroid titles.