(i.e. if the borrower was to default)What i found particularly appealing about the BRRRR method was the "velocity of money" or the fact that I could repeat this process several times and quickly. 

You don't have to... but this will keep your velocity of money high. 

This is primarily due to the affects from the time velocity of money.

If this is the case, see if you can use HML or PML to maintain your velocity of money and close like cash. 

I've thought about this same thing and I've kicked around some ways to apply the Velocity Banking concepts to real estate investing. 

I'd also really like to know what everyone thinks about the "velocity banking" strategy, wherein you "pay off your mortgage in 5 to 7 years" with a HELOC.

If you want to get some velocity of money going, consider a refi to free up cash and move this cash into another investment. 

They're also pushing the "velocity banking," which I'm not convinced is the best strategy to "pay off your mortgage in 7 years."

I could wait for the 6 month seasoning period and increase my ROI but figured the velocity of money is more important at the moment.

It helped me understand the purchasing of 1 asset at a time and the velocity of equity.