I had threaded shocks on my LST shocks and loved them, its the only thing Id carry over from the LST's to my big bores.
Myself, not a racer, love threaded shocks, the spacers are a pain in the butt, if your scatter brained like me you always lose them, my LST threaded shafts never seized up with dirt even running in the thickest of mud and the finest of dry dust, a quick brush with an old toothbrush after each dirty bash sorts them out ready for next time.
You don't need a caliper to adjust threaded shocks unless you require 1:1000" accuracy, just a rule or even a piece of card/paper with the distance from bottom of the cap to adjusting collar marked is all thats needed to get them all the same.
HPI don't need to make a whole new big bore shock with threaded bodies, just an option part threaded alum body for big bore/flux owners that want them, I believe there is a big gap in the market for them.
The only thing I didnt like with threaded bodies was after a while with all the vibration the adjusting ring would be way off where you set it, so I ran two sets of rings per shock, one for adjustment and another directly above it to act as a locknut to prevent the adjuster ring vibrating and moving up/down the body.