Seeing rank is just a crutch, it shouldn't matter what the opponents rank is at all.
All it does realistically is give you yet another reason as to why you believe you lost, it's meaningless to see their rank- fight the match, win or lose just continue.

To be able to enter a rank you should be able to defeat those that have already entered said rank, that's how actual ranking systems usually work- so yes, you should be able & forced to fight those that have reached the ranks above you & they should also be able to continue playing ranked if they desire because at the end of the day there isn't much else to do on Naruto once you've finished your dailys except plop around in the Arena.