perhaps. We will have to see.
I would have a couple of concerns with letting the default arrows be random. I think a lot of people might not realize these consequences:
First, if non-random arrows are stronger as deemed by many players, then it could be seen as beneficial to be constantly targeting single units with buildings, which would be a pretty sub-optimal scenario. In addition, we might have to balance buildings both in their capacity to target random units (how they are currently balanced) and in their capacity to target single units (what makes them strong in 26.6).
My last point is more on appearance: I don't like the idea of completely changing the way the arrows function upon a click. It just would look and feel clunky and possibly counterintuitive. (Opinion if you can't tell :D)
I am certain that the issues a lot of people have with defaulting to the closest unit are really just balance concerns and can be addressed by modifying building arrow count (default and max arrows) and damage. However, if everyone agrees that what @wowgetoffyourcellphone suggests is the best way forward, I would begrudgingly concede.