I'm not trying to be "broken", just make a monk class better, it seems like one of the weakest core classes.
It is exactly the weakest of the Core classes. Believe me, you don't want -2 to
all attacks just to get
one more, and that with reduced damage. Improved TWF requires Dex 15, Greater TWF requires 17, pushing your already bad MAD.
Making a Monk look OK is possible, but needs some MAD reducers (like Intuitive Attack or whatsitcalled), some alternate class features, and a different approach.
Flurry is good, granted, but if you
have to make a full attack to do damage, this makes you less versatile again. First and foremost, see if you can boost your damage. This means size increases and the Improved Natural Attack feat for large damage dice. Next, you'll need a way to do even more damage. There's an alternate class feature around which replaces Flurry of Blows with the ability to make a single attack for double damage as a full-round action. This one is a beauty combined with a method of generating lots of Attacks of Opportunity, like Karmic Strike or Robilar's Gambit.
If you want to keep Flurry, definitely look into the Fist of the Forest and Shou Disciple PrCs. Those offer full BAB while progressing Monk abilities. Shou Disciple even offers the ability to apply Flurry of Blows to martial weapons. Choose the right weapon (like a Guisarme or other reach weapon) and go to town.