I have a few ideas:
How about more light in the game? Even if just in the arena, it seems like you are fighting very often in the dark against opponents who inevitably can all magically see in the dark (because AI).
...
Beyond that, how about graded 'challenger' mode where your rank in comparison to the opponent's determines the prize? Imagine master vs inept barely earns tuppence for winning, whereas inept vs master promises several pounds as the ultimate treasure!
...
Weapon quality. Remember the two meat cleavers? One's rusty and rough, the other shiny and sharp. Now imagine a few versions for each weapon, but properly so within the same rank, not to be confused with the rusty sword at novice vs the adept swords. You could have 'exceptional' weapons which obviously cost a lot more than standard variants and offer better stats, which don't have to be extreme.
...
MY BIGGEST AND SIMPLEST WISH, arena opponents using varying quality equipment just like you do. Fight against someone who could only afford an old worn gambeson, or perhaps battle against a knight wearing exceptional plate, you can end up with all sorts of varieties. Clearly it can be homogenous throughout the opponent (like low quality everything, standard everything or good everything), because I notice they already do that with colours.