This suggestion is simple. When you open fire on a wanted target before your scan finishes you currently get an assault bounty. This can be rather annoying, especially for mining and trading ships who are often the target of piracy. You end up being threatened by a pirate and when you try to open fire first you get wanted because you didn't wait for the scanner to finish scanning them. Now you are locked out of the entire system and kill on site for all cops. Because you shot at someone trying to rob you.
Instead of this, if you open fire on an unscanned ship and that ship IS wanted, instead of getting an assault bounty you would get a "Premature weapons discharge" fine. Fine's are a lot easier to deal with, so while the fine will still be an inconvenience, it isn't overly punishing for an understandable mistake. If the ship isn't wanted you still get an assault bounty.
Instead of this, if you open fire on an unscanned ship and that ship IS wanted, instead of getting an assault bounty you would get a "Premature weapons discharge" fine. Fine's are a lot easier to deal with, so while the fine will still be an inconvenience, it isn't overly punishing for an understandable mistake. If the ship isn't wanted you still get an assault bounty.