I am considering attempting my own nozzle design. What do you think of one of these metals laying horizontally and holding 1-2 heater cartridges for the bottom part of a nozzle? Sliced into a reasonable length, of course.
Technically speaking, brass is not a good material for anything that should conduct heat, so I’d suggest aluminum instead. If you need inspiration for the design, just look at E3D’s drawings and build it exactly like that 
There are reasons most heads use aluminum. It’s a good heat conductor, it’s cheap, and it’s easily machined.
Brass is harder, and not as good a heat conductor. If you’re planning on skipping the inner threaded guide, then you might want brass for its hardness so it takes a good thread and can be polished well on the inside. Otherwise, I’d go with the typical aluminum heat block with the threaded brass tube inside.
How about copper then?
Copper would be a nice material for thermal parts as well, but is heavy and expensive. And tricky to machine.
Good point @Thomas_Sanladerer - I forgot about the weight of brass/copper.
@NathanielStenzel - Remember: this hot end will likely be moving, so weight is a factor.
How about a copper washer under an aluminum block with a bronze sheet wrap around the aluminum block? This should direct more heat to the bottom of the nozzle via the copper.
Copper is an absolute arse to machine. Avoid.
Aluminium or brass is good.
Brass machines more nicely than aluminium, and you get a smoother nicer surface finish, which means less gunk sticking to the nozzle. Aluminium is lighter and more conductive however.
Ideally aluminium block heater, with brass nozzle.
Copper washer = no machining
@NathanielStenzel I’m not sure if i understand you correctly, but if i do, the copper will help to spread the heat over its own cross section but it won’t speed the heat transfer. It’ll actually slow it down because it adds two extra interfaces. If you’re using the bronze to insulate, you’d be better off using ceramic insulating tape with kapton. It’s cheaper, easier to use, and a better insulator than bronze. You can get it at the qu-bd web site. Copper heat spreaders are usually used to spread a point heat load to a large base of a heat sink, in an effort to provide a more uniform heat gradient on all the fins. It won’t really be effective in focusing heat, the insulation would be better at that.