I'm trying to figure out why someone would want 5 rushing QB's to run the ball 100% instead of just getting 5 RB's... If you really wanted to you could split the carries between your QB, HB, HB2, HB3, and FB. QB's tend to cough up the ball and get injured more frequently. It's not realistic to expect to run with QB's 100% of the time and be effective, in any era. You can say as much as you want about the size of your line but size typically comes at the cost of speed and DLineman and Linebackers aren't exactly pushovers. Add in the fact that the defense can utilize their hands and there's no reason why you should realistically expect 4ypc or 5ypc running with a QB 60x a game. To put things in perspective the best running QB in the league, Lamar Jackson, has fumbled 5% of the time he gets hit. Derrick Henry averages a fumble less than 0.8% of his hits. That means you're more than 6x as likely to fumble with Lamar Jackson as you are with Henry. In addition, Henry averages 4.9ypc for 16 carries per game. If you take out his first two years where he was underutilized he's averaging 20 carries per game and still holding strong at right around 5ypc. Lamar Jackson is averaging 6ypc with 10 carries a game. Expecting Lamar Jackson to maintain that ypc when it's doubled or tripled is not realistic, especially when the D knows it's coming.