Apparently, I forgot to close this. The code has been merged and pushed.

I think issue236 explains the original motivation behind OptionFlags. So if you
want to get rid of it, my recommended starting points would be:

1) Read the discussion of issue236.
2) Grep the code for occurrences of OptionFlags
3) Check if these are all legitimate uses of OptionFlags.
4) Check if your suggested replacement would work equally well for these cases.

Citing a TODO from the code, I'd like to see if we can "get rid of OptionFlags, 
instead use default_value = "None" ?".