No. The agression we see from wasps is in defense of the nest. They will still aggressivly defend their nest regardless of how well they are fed.
If anything, better conditions will allow them to reproduce more quickly and cause an even bigger problem in the form of more nests in a smaller area.
As far as having them forage in your yard, no problem. Just like foraging honey or bumble bees, they are non-defensive when away from their nest.

definately do not feed them, you will only attract more. If you know where their nest is, sevin dust is a good way to kill yellow jackets and wasp.

This will work, even in there nest they will be far less aggressive, but you may find that its not worth it. The population will grow and you will spend a lot keeping them full. I had a smoke house collapse this summer and lost 2 salmon to the lawn below (an 8 lb fish and a 6 lb fish, cleaned headed and boned) it took roughly 40-100 (fewer at first, more later, hence the spread) yellowjackets 5 days to clean up the mess. when they are full they can barely fly. Part of the problem is that yellow jacket foraging behavior is very off-putting they buzz in close and inspect you, because they can smell you and can tell you are made of meat. The unease and tension leads to poor human behavior and a sting, that or someone foolishly steps on the clearly marked nest buried in the underbrush and the lean colony members capable of flight take off with a bloodlust unrivaled in the civilized world.