If you put two cogs on the AW driver, the larger typically with three teeth more than the smaller, you can split the difference between gears, for six evenly spaced gears and a modest increase in overall range. The resulting 6-speed has a slightly wider range, with closer spacing, than an FW four speed hub; but it is not as wide as a five or seven speed hub.

The best thing is that it's not at all complicated. The driver on the AW has room for two cogs, and since they are normally dished anyway, you simply dish them away from one another and the spacing is right for a derailleur system.