I don't think I would mind this.

http://inhabitat.com/guerrilla-grafters-secretly-graft-fruit-bearing-branches-onto-san-francisco-trees/

Saw that some time back, I thought is was a fantastic idea!  I might start doing that around town myself, there is a lot of crab apple here that could use some real apple branches.

Hi,
Did you know that some phytos are ok for non fruit bearing trees, but not for fruiting trees because the product will reach the fruit ... and make them improper to human consumption ...
So although the first idea is good, the result could be a drama by intoxicating the poor lad that would dare to eat the fruit.
In the wild, though, that could be an idea ... that I've been thinking of ... One day perhaps ...
The problem with fruit bearing trees is that people would break the branches to reach the fruits... and thus destroying the tree.

Grafting is a lot of work to get right and that is only the first step then you need to maintain the graft. 
Proper ongoing pruning and support from wind damage the 1st year ...  You may just end up damaging the tree unless you will keep maintaining the graft year after year.

Also local wildlife may depend on that wild fruit for their winter foraging.  They may not appreciate a consumer variety that does not produce and last as well.