[Taqwus]

Basic encumberance does drop a point at the fifth star of experience, if memory serves, while some lighter weapons get you multiple attacks per round. Strength impacts efficiency somewhat through damage (although even some melee weapons don't benefit from strength -- whips and Rod of Death for examples).

There's no real modeling to make strength impact attack frequency other than making it very hard to damage somebody unless you had strength, and you can't make an item benefit more from strength (ex. base damage -60, strength bonus 5*str -- negative damage if below str 12, but a whopping 40 damage if str 20). Which would be interesting if allowed. *shrug*