adding drives / growing RAID-10?

I was wondering if "adding drives / growing RAID-10", similar to the same feature available for RAID-5, was ever contemplated by any of linux-raid developers?

What would be needed, at least in theory, just to add one disk to RAID-10 array?

I assume having to temporarily add "N * 2 + 1" drives (where N is the current number of drives in the array) just to add one drive to RAID-10 is the worst-case scenario.

Tomasz Chmielewski