If you are cutting hard brass then you can make cutters from silver steel (drill rod) and you don't need to harden them. If you do harden them and they get hot they will blunt, but you can let down the temper, re-shape them and harden them again. So you could make cutters to suit whatever thread form you need. I wouldn't call them single point, but more like the thread milling cutters already in use.
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I wouldn't worry so much about the motor, but think more about the design of the spindle, then use a belt drive to connect it to a motor. Buy an ER11 collet holder on an 8 mm shaft and fit it into some ordinary ball bearings, in a bock of Ali, easily made by dowelling and bolting it to the cross slide and boring it through with drills and reamers in the main chuck. Height and alignment will be correct. Then you can make cutters with shafts up to 7 mm, or smaller as convenient. Then maybe fit the motor alongside or above the spindle. I don't think it would need much power - you can always take it slow.
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The other problem is to hold the thin wall components without distorting them, but I imagine you have already worked that out. The same spindle can be used with ordinary milling cutters to make spigots and nests to support the rings.
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Then you might find yourself building a whole new machine based around a rotary table, once you have developed your ideas further. A friend of mine did a lot of complex machining with a rotary table mounted on a mill - without CNC - but he spent time planning the jobs on CAD first.
