To save data about how exactly and where these arrows been rotated you can store coordinates of corners where these arrows been rotated for 90 degrees. Like this:
I like this shape of arrows better, it looks less chaotic than the current ones. And the slight rounding makes their design more modern and pleasing to the eye. +1 for this Feature Request.
bump. PLEASE can we fix the godforsaken arrows, obsidian? Canvas is so close to greatness, messy arrows that you have little control over are like the one think holding it back.