I really think a offense that had a back or two that ran the 4.7 40 or so but came in at 245 to 260 and had power could thrive again, everyone is so light from the Ends to the LB's, have a good interior Line that could push and a back like that would punish everyone else. Sure the 60 yard break aways may not be there where he out runs DB's, but you would have a steady 5 yards to 15 or 20 yard occasional burst runs. Defenses would be beat up and tired, your passing game would flourish since they would have to commit safeties to help those 230 pound LB's tackle him.
Bettis, Means, George, Okoye, Riggins, Csonka, the freak known as Bo Jackson, so big so fast, the enigma Walter Payton, not big to look at, but punished you like a 250 pound guy every run, Campbell, oh and Jim Brown who was bigger or as big as Linemen in his day, Throw in Lynch to this group. All these guys tough, very few had top speed, but all would deliver a blow before they took one, running thru, over or carrying tacklers with them.