I haven't tried using a larger chainring and wonder if this would affect the foldability. My calculation suggests that extra 6 teeth increases the chainring diameter by about 24mm and you could do a visual check on the implications of this. A longer chain would be needed which might affect how easily it can be folded.

You are correct that a larger chainring will give a higher speed at a specific cadence and this applies through the whole gearing range. 58T instead of 52T increases the gearing by about 11.5% which is close to 1 step in the Rohloff gears. If you live in a relatively flat area with no need for the bottom gear or two then I would suggest that you try using a bigger chainring if only to find out if it works.