What is so complex or bothersome if weapons have 1-3 keywords listed next to them? They could even be listed as "Optional Properties" in the table, or even as a separate rules module. Or maybe they would apply to whole weapon groups, e.g. 'Flails: you get +2 on disarm and trip maneuvers. Heavy flail also has 10 ft. reach'.
The problem is once you start adding things like this to the game then it often becomes what the game is about.
I found my 3.5e games got bogged down a lot by small modifiers that weren't all that complex. But there were so many of them and they were such a small bonus that they tended to get forgotten on a regular basis. Whenever someone forgets to apply a modifier, however, my players love to point out how much smarter they are to the other players so that was all combat ever became:
Player 1: "I trip the monster. (rolls a 12). That's 20 total."
Player 2: "Wait. I know you have a 16 strength and a 5 BAB, so isn't that 22?"
Player 1: "Plus 3 for strength, plus 5 for BAB. That's 20."
Player 2: "Aren't you using a flail?"
Player 1: "Yeah? So what?"
Player 2: "All flails give +2 to trip attempts."
Player 1: "What? I didn't read that."
Player 2: "Yeah, it's right here. Flails give +2 to all trip attempts."
Player 1: "Hmm, I didn't realize that. Fine, then it's 22."
(Next turn)
Player 1: "I trip him again. (rolls a 10). That's 18 total."
Player 2: (only half paying attention to the roll) "Did you add the flail modifier?"
Player 1: "Crap. I forgot. That's 20 then."
(Next turn)
Player 1: "I trip again. (rolls a 10). That's 20 total."
Player 2: (only half paying attention to the roll) "Remember flail?"
Player 1: "Yes. I rolled a 10, plus 5 BAB, plus 3 strength and 2 from flail."
Player 2: "Ok, ok. I was just making sure since you forgot the last 2 rounds."
Then repeat this process for every modifier in the game....in every round of combat in the game.