Essentially, you would be making Power Attack the feat around which combat revolved to the extent that melee combat would be even worth it at high levels of play, and more or less telling your players not to play anything but spell casters.
Extra BAB would just make Power Attack that much more important.
This is such a huge reworking of the game that I can't foresee really how the game would play out with this change, so its hard for me to give advice. Adding bonuses to the attack rolls would totally change the game by making AC much less important. Adding scable damage with character level (probably a better choice) would make critical hits that much more important, scale the random factor in damage rolled down much further than it is already at higher levels of play, slightly deemphasis strength, and I don't know what else.
But, if you really want to experiment with this my completely off the cuff suggestions are, Power Attack becomes a manuever - essentially every class gets it as a free feat. Plus, all creatures get a +1 dodge bonus to AC for each full +5 points of BAB they have provided that they are armed and not flat footed. Classes/monsters do +1d6 damage on all weapon (not natural) attacks for each full +5 points of BAB they have, and rogue sneak attack damage goes up to d8's (from d6's).
You'll probably have to do some reworking of the Fighter too. Change the feat progression to 1st, 2nd, 4th, 5th, 7th, 8th, 10th, 11th, etc. Weapon Specialization gained for free at 4th, 8th, 12th, 16th, and 20th and upgrades of a previously selected Weapon Specialization to Greater Weapon Specialization at 12th and 20th.