Hm...
For type changes, I can see...
Steel should be SE against Flying. Rock hurts birds because it's harder than their hollow bones. Steel hurts Rock because it's harder than Rock. So why doesn't Steel hit birds for extra damage?
Poison should be NVE against bugs if bugs are NVE against Poison. Because most bugs either resist a kind of poison or are very prone to it, if bugs are NVE, so should poison, because right now bug isn't SE against Poison. They should both have the same matchup.
Dark should be NVE against Ghosts. Ghosts love the dark. Psychic should be SE against Ghosts, and Dark SE against Psychic to fix the trio.
Fighting should be SE against Bugs. It isn't very hard to squish a bug.
Flying should not be NVE against Electric. Somebody explain that to me.
Flying being SE against Grass makes sense to me, sort of. Birds can peck at leaves and rip them up very easily (and much easier than other types) and birds make trees into their homes.
Fighting is NVE against Poison and Poison is normal against Fighting. That needs to be flipped around. Strong people are harder to kill with poison.
Bug being SE against Dark and Psychic makes sense. Pokemon of those types are more likely to be intellectuals (such as Alakazam), and intellectuals usually don't like filthy things, or being forced to touch spiders or bugs... Like me...
I think Rock is SE against Flying because people throw rocks to hurt or drive away birds. "Kill two birds with one stone", that kind of thing. Of course, you can hurt birds by shooting them with steel bullets too, so yeah, Steel should be SE against Flying. Good point.
However, I don't get your point about Bug vs. Poison. Bug is NVE against Poison, so Poison should be SE against Bug. If all types interacted in the same way, Fire would be SE against water.
Fighting SE against Bug makes sense from a flavor perspective, but does Fighting really need a
sixth super effective hit, and a neutral hit on Poison to boot? Also, you just made Scizor cry by giving him a 4x weakness to two priority moves. He's in his room now, screaming "It's not fair!" and Bullet Punching his pillow. I hope you're happy!
Flying is NVE against Electric because...well, have you ever seen a bird try to sit on an uninsulated power line?
@Artix: #1 - Watch your language.
#2 - Please don't try and tell me that Gamefreak has thrown common sense out the window, just because a few of their type combinations are a bit of a stretch.
#3 - So, Bug would have 4 weaknesses. Celebii has 7, and it still rocks.