Yeah, protection I think you'll be fine and probably better. Believing it will be somehow cooler is probably wishful thinking. The oxford shirt will probably be some kind of layered and woven fabric and the vest will prevent the escape of heat in the torso, where most of the body heat is. I have and I know this is excessive and I'm getting help for this problem but have 7 jackets of different materials and on hot days my dianese ventilated and mesh jacket that offer good torso ventilation will be the one, no doubt about it. Torso ventilation is key to keeping cool and the vest, well I personally don't think it will accomplish that.

 

They make all sorts of moto jackets for warm weather. They have jackets that are 100% mesh, they're called air jackets. But even with heavier jackets, all the vents on them allow you to stay surprisingly cool in hot weather. Also, on some level the jacket helps keep you cool (as long as you dont but a dark color) because it keeps the sun off you while still allowing the wind through.