I've been thinking about whether it'd be possible to get the chainline right with a wheel that has fixed/geared flip flop. The chainline might be a little easier to sort if you use a 5/6 speed rather than 7/8/9. I prefer the look of the older 5/6 freewheels anyway. For the chain, you could just magic link in the extra section for when riding geared, then take it out when riding fixed.
I've been thinking about whether it'd be possible to get the chainline right with a wheel that has fixed/geared flip flop. The chainline might be a little easier to sort if you use a 5/6 speed rather than 7/8/9. I prefer the look of the older 5/6 freewheels anyway. For the chain, you could just magic link in the extra section for when riding geared, then take it out when riding fixed.