This is in pretty much as I described: A new option exists that determines whether or not you receive "reckless fire" warnings for aiming a projectile at a target with allies behind it.
Worth noting: Even if this is turned off, you will still be warned if the "reckless fire" could potentially cause a capture objective in progress to fail (such as by hitting a target that turns friendly during the capture attempt.) I figure even though the chance is still low that it will actually happen, it's serious enough to still warn over, even when the warning is turned off in other cases.
Also: Apparently my default target suggestion code, if these warnings are disabled, will begin selecting "reckless" shots as possible default target positions.
I'm letting this go as a pleasant side-effect for now (after all, if you don't want to be warned over them, presumably you also don't want the targeting UI to avoid them), but if it becomes a problem I can look into disabling this.
Thanks again for the suggestion and feedback.