Sounds like a bad idea to me, most everything is a con. Cost, awkwardness, more recoil and little to no more accuracy. Have you seen Hickok45 shoot the short barrels out to 80 yards and beyond?
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek