To bring a flight attendant upfront creates many other issues.
Name one...just one.
1/ The 1 pilot + 1 cabin crew hijacker scenario ( unless you want to start vetting cabin crew in the same manner as we do pilots......cabin crew don't even do one on one interviews in some airlines, they do mass interviews......hardly the same standard)
2/ Distraction. How many pilots have been distracted by conversation with the cabin crew and missed position reports or a looming CB while they are organising their post flight drinks session? I'd suggest quite a few, I know that both myself and my Captain missed top of descent once when we had a particularly attractive young lady up front with us. When I go to the loo and I have a good looking twenty something male First Officer who is green on type, I know I return as quickly as possible if the cabin crew member who goes in is a young and attractive female. Distraction.