I guess the way I look at it is this - an "exploit" is something that gives one side an unfair advantage over the other.

So if 24lb cannons can overshoot thier range - both sides can use that.

If it were something that only one side can use, I would agree that it is an exploit, and should be banned, but since both sides can use it, what's the issue?

I've been in some truly Great Games where both sides open up by peppering each other's line with shrapnel shot for a few minutes before advancing the troops.