The ignition connector is the same as gen1 / gen2 busa, so a toggle switch in place of key would be easy, obviously with no theft deterrent and more of a drag bike thing.
I've done the red kill switch as main power on/off on gen1 and gen2 busas plug and play using a relay so all the current for the key switch doesn't go through the red kill switch, but haven't done it on the gen3 yet. I have the connectors here for the ignition and right hand control of the gen3, so pretty sure I could make the red kill switch operate everything, but on a brand new street bike would seem a little odd to me, makes sense on a drag only stripped down bike etc.
At least the ebay ignition switches I use on my electrical test boards, they weigh 17 ounces, with no wires just the connectors needs to plug into ignition and male/female the RH control connector plus a relay is 3-4 ounces. Thats with no wire, to me doesn't seem like the greatest way to cut weight IMO.