Being inspired by videos of English potter Jim Malone throwing, I have come up with some plans for a similar type wheel, which is a hybrid of a traditional kick wheel (or Continental Wheel) and a traditional Korean wheel. Here are the cut away plans...very simple design that can be adapted to any size thrower. In the case of Jim Malone, he has raised the wheel head up maybe 6" or more using blocks of wood attached to the wheel head, making it a more comfortable height on the back.
Essentially, this wheel can be made at any height by lengthening the center portion of 1" solid steel rod and the 3"I.D. steel tube.
Rather than fabricating a top point from hardened steel, my solution is to adapt a "live center" with built in bearings from a metal lathe, cutting off the morse tapered shaft. They are cheap, made with extremely high tolerances, and are hardened steel = perfect! The receiving cup should be simple to fabricate for a piece of the 1" steel shaft, drilled with a counter sink on the drill press, heated up to red with a torch and dropped into water to quench (to harden the mild steel). This cup is then welded back on to the top of the shaft.
I envision the flywheel being in the 30 pound range, with compartments so that weight could be added. It could also easily be poured concrete for more weight, but I think the flexibility would be better.
Here is what a "live center" looks like...three bearings inside. Just cut off the shaft and mount the body into the wheel head. Can be bought for as little as $10.