I would stay away from the Nulco brand. I also would not recommend the ones that use halogen bulbs. If you like that Kichler one you can get it here and use coupon K15OFF to get 15% off.

Overstock has lots of fixtures in your price range. I like your idea of constructing something of translucent material to diffuse the light from the existing fixture but that sounds like a tricky project! Our main floor bath is smaller, maybe 5 x 8, but a two-light fixture provides plenty of light (including the tub/shower). Our fixture overhangs the mirror so the light seems to be amplified. I'd think that either 3 or 4 bulbs would provide the light you need. Maybe looking at photos of baths can help you decide what style you like. For example, do you prefer something linear or something with curves, as shown in this example? Here is a link that might be useful: Another Overstock option

your electrical is buried behind the cabinet, that is illegal, sorry for the Karen moment, but that is a bit no-no, also very limited on what can cover that up as the wires will be exposed and the plate is not designed to have stranded wire run to it. Show me a top down view... I can help you but I need a more clear vantage point.

the first one is better than the second one, but if i was going to mix metals with nickel, it would be bronze not brass