I haven't been paying attention much but do the traders online upgrade their trading wares as you level up?
No, it's always the same stuff, but it does shuffle around every day.
Also I think that trading with higher rank with lower rank hunters might make it easy for the overall group to complete quests
That's a problem in itself. The low-rank is where people should be learning how to play the game, and loading them up with the best gear means they can get smacked around by monsters without fear of getting killed. If players don't hone their skills in low-rank, they will not survive later on. You know the old saying, give someone a hunt and they complete a quest for the day, teach them to hunt and they complete the entire game. This is why I no longer fight much in low-level quests, I usually let the others battle, and step in only if things aren't going well.
Besides, half of the reason to play is to strive for that next suit of armour or that next great weapon upgrade. If all that is just handed to you, what's the point?