to answer some of Pat's questions, here's my observations...
1. i've never had Jim's adapter slip or move on me, so i don't think width is a big factor.
one thing i would like, is more lateral adjustment. i've had a few builds where i have the adapter as close to the spokes as possible to get the clearance and alignment i need. it just needs longer sprocket prongs. not much longer, just a little.
2. i like steel sprockets. i've got some aluminum ones that look like sawblades after only a few months. with a high performance build, they really take a beating. since most sprockets are for smaller chains, a HD #41 chain and a motor with a lot of torque deforms the soft aluminum teeth.
3. annodizing's always a cool option. i was gonna get one of mine annodized, just never got around to it. if i coulda bought one already done, i woulda paid extra. but, not
much extra, 'cause i know what annodizing costs (if i had a workshop or a big garage, i'd do it myself
)
4.i don't think you need to make every size possible, but definitely more than just a couple. i ride 28's and 30's, and want one even smaller for flat out top speed, regardless of the low end sacrifice.
on most other bikes, the difference between a 40t and a 41t is about an inch of chain and 1mph, so every tooth count isn't really needed. i'd make common sizes, 30, 36, 40, 46, 52...
having the option to buy any tooth count would be nice, too, as long as the cost to make a one-off wasn't too crazy.
now here's some input from me...
for no other reason than to avoid controversy, i'd try to make it look a little less like Jim's. i know it's a basic design with not much room for aesthetics, but, y'know...
i'd make the sprocket bolt pattern universal. i dunno what Andy's, or some of the other makers are, but the ability to use a kit sprocket, or any other sprocket gives a lot more options. i have a 35t from, uh, i forget, that doesn't fit anything but a rag joint, even though it has 50 holes drilled in it. so it's useless to me.
with a universal pattern, not only could you tune your gearing easily, but in the event you slip a chain and mangle a sprocket (which i've done) you can still slap your kit sprocket on to keep you riding while you wait for a new one to ship.
with very few exceptions (mostly on older bikes) the sprockets are all standardized so they can be interchangeable and invites competition and variety.
i think that's about it...