7 cogs on a Uniglide 6 hub?

Seems there are a lot of threads outboard the small cog on my Exage Uniglide 6 hub. Any ever add an extra cog there? Or are there some non-apparent consequences asside from only 6 indexes.

I have been using a uniglide wheel with a Turner all wheel drive system so I have to sacrifice a cog anyway as the takeoff to drive the front wheel, so adding another cog could return all 6 indexed gears while keeping the innermost cog as a takeoff only.