Probably the first thing I would change would be the Nonlethal Damage rules. Here's what I use:
NONLETHAL DAMAGE
Dealing Nonlethal Damage: Certain attacks deal nonlethal damage. Other effects, such as heat or being exhausted, also deal nonlethal damage. When you take nonlethal damage, keep a running total of how much you’ve accumulated. Do not deduct the nonlethal damage number from your current hit points. It is not “real” damage. Instead, when your nonlethal damage equals your current hit points, you’re staggered, and when it exceeds your current hit points, you fall unconscious. It doesn’t matter whether the nonlethal damage equals or exceeds your current hit points because the nonlethal damage has gone up or because your current hit points have gone down.
Staggered and Unconscious: When your nonlethal damage equals your current hit points, you’re staggered. You can only take a standard action or a move action in each round. You cease being staggered when your current hit points once again exceed your nonlethal damage.
When your nonlethal damage exceeds your current hit points, you fall unconscious. While unconscious, you are helpless.
If the damage equals or exceeds the target’s massive damage threshold, the target must make a Fortitude save (DC 15). If the target succeeds on the save, the target is dazed for 1 round. If the target fails, he or she is knocked unconscious for 1d4+1 rounds.
I find that this combination of D&D and D20 Modern works great, especially if you're running a boxer-type character.
What I wouldn't change: The d20 Modern Base Classes! Genius.
NONLETHAL DAMAGE
Dealing Nonlethal Damage: Certain attacks deal nonlethal damage. Other effects, such as heat or being exhausted, also deal nonlethal damage. When you take nonlethal damage, keep a running total of how much you’ve accumulated. Do not deduct the nonlethal damage number from your current hit points. It is not “real” damage. Instead, when your nonlethal damage equals your current hit points, you’re staggered, and when it exceeds your current hit points, you fall unconscious. It doesn’t matter whether the nonlethal damage equals or exceeds your current hit points because the nonlethal damage has gone up or because your current hit points have gone down.
Staggered and Unconscious: When your nonlethal damage equals your current hit points, you’re staggered. You can only take a standard action or a move action in each round. You cease being staggered when your current hit points once again exceed your nonlethal damage.
When your nonlethal damage exceeds your current hit points, you fall unconscious. While unconscious, you are helpless.
If the damage equals or exceeds the target’s massive damage threshold, the target must make a Fortitude save (DC 15). If the target succeeds on the save, the target is dazed for 1 round. If the target fails, he or she is knocked unconscious for 1d4+1 rounds.
I find that this combination of D&D and D20 Modern works great, especially if you're running a boxer-type character.
What I wouldn't change: The d20 Modern Base Classes! Genius.