Wow 250A sounds like a fun project! I'de like to change your mind about needing 1/16microstep for a cnc or similar machine.

Lets pretend I have a screw that takes 10 revolutions to complete 1inch. A stepper motor that takes 200 full steps to complete one revolution.

If I use 1/16th step it will take 200(steps)x16x10=32000steps to complete 10 revolutions and go an inch. Now you just take 1/32000 =.000031inches which is your resolution. Lol that's a really high resolution. Even at full step resolution is good at .0005 inches...this will vary with your threads per inch/meter. Microstepping is definitly needed though as it makes everything much smoother and you have control over your resolution but I see no reason to go super high with microstepping. Unless you have 2tpi and want .0001 then it is very usefull...now I'm curious what microstep are all of you using on your machines right now?