That's a false equivalency. You're comparing a narrow range of carries against any other RB without those parameters. Compare apples to apples or don't make the comparison.
If those are apples to apples comparisons, I'd like to see where you got the numbers you're stating. I'm looking at his season stats and he's never averaged less than 3.9 yard per carry. His last 3 seasons were 4.9, 4.3 and 4.6. His career average is 4.3. From 2011 to 2015 he lost 2 fumbles.
I'm not saying Ingram is great, but he's a good back who can block, catch and run and is a good fit for the type of offense we run. I think your tweaking of statistics is not a fair gauge of Ingram's overall performance. No one will be a 20 carries per game back, not even Fournette, if Payton continues to call games the way he always has. It's an unconventional offense which makes it hard to judge the value/performance of backs.
I'm all for letting Hightower get the bulk of the carries if his performance warrants it. Just keep in mind, he had 26 carries for 102 yards for a 3.9 average, which, interestingly enough, is Ingram's worst season average. I'm not knocking Hightower at all. Seattle is tough for anyone to run one, as evidenced by getting stuffed when trying to run the goal line offense.
I'm just saying a lot of people are overreacting to the fumbles, which are a legitimate issue, but a statistical anomaly when considering his overall body of work. His calling card has been his versatility, football security and pass protection. These are the things that make him valuable and difficult to replace. We've seen what happens when we put a back in who doesn't know what he's doing and end up nearly getting Brees killed back there.
When it comes down to it though, I'm ultimately in Payton's corner with however he decides to use Ingram. I suspect we'll see more running by committee. Time will tell.