Really!!  

It's not that simple.

Yes it is!

What about when your at home checking weather before you come in, that's a flight duty.

When you are home checking the weather, if it is part of your offical preflight duties, you are on DUTY!   If it's just to check the weather for youself, then it is not DUTY.   If you are required by the company to check the weather from the house, it is DUTY!   Your duty clock has started and you'll be required to show you've had 10 hrs of REST in the preceeding 24 hours from the reasonably planned completion time of your Part 135 flight.

Or when your company mandates you come in early and does not pay you, that's flying duty.

That's duty also!   Duty is not pay.  Duty is DUTY!   Your pay issue is a matter between you and HR.  The FAA, however, is looking for DUTY TIME.

This is why we have an issues, companies abuse, employees try to make it work, and it equals not a good choice.

Making a super complicated regulation who's flowchart has more turns than a Pac-Man game matrix isn't going to fix your problem!   The current system is very simple and thorough enough.   You, obviously, are just not following it!

People abuse this all the time which leads to a lot of accidents, including pilots who should be sleeping or resting on their night shifts, then coming into work tired.

Stop abusing it then.  You are on DUTY whenever you are working for the company, or have an obligation to respond when called (RESERVE/Beeper or phone calls).   Again, the problem is not the regulation!