I understand what you are trying to do, but ... I think the design of the Xtreme was a bit of genius engineering. Almost EVERY bit there is essential. Sure, some of it is steel and could be reduced in weight by changing the materials, but actually removing it - rather unwise imho.
The burner plate: replace with titanium maybe. Remove totally - risky. Upset the flame pattern and the heat radiation pattern, and possibly make the stove susceptible to 'flash-back'. That's something you do NOT want.
The brass tube: CRUCIAL to the performance of the stove, as is the thin brass rod inside it. This tube is the real heat exchanger, not the bit sticking up into the flame. The bit in the flame just collects heat and passes it back down to the straight section. Took me a long while to figure this bit out.
The flattened tubing supports: heavier than Ti, but Ti would sag under the red heat. They are not that heavy in reality.
The legs: good luck reducing the weight of those without weakening them too much. They are either Aluminium or magnesium - can't remember which.
The big spring: maybe, but keep all the spring pressure as it controls the mechanical stability.
The connector to the canister: I know this has been machined down to reduce its weight, but that can be a bit risky. It collects some radiant heat from the stove to assist in the boiling of the fuel. It also provides the needed mechanical strength for the mating process.
Black control knob: yeah, reducible. But not a lot in it.
Brass control valve inside: be very careful about touching this. The design has a few secrets associated with keeping it clear of gunge.