Random idea I don’t think anyone’s thought of: how about an air-filled cricket wicket with a flat back which sticks (temporarily) in some way to a wall? The (lightweight – perhaps inflatable) bails rest on top of the stumps with small holes underneath. When the ball hits the stumps, a puff of air is created which blows the bails off. The stumps would probably be linked for convenience and air distribution – either at the base or (probably easier) just below the bails.
Often kids play cricket against a wall because it saves having a wicket-keeper, and you can play in a smaller space. But that means conventional static wickets won’t work, as they can’t be knocked backwards, and chalk wickets can’t have bails (obviously). However, something made of e.g. thin flexible rubber, just strong enough to keep its shape under normal circumstances, which converted the hit of a ball into an upwards puff of air would give you the ability to be out (or not) in the conventional manner. No more arguments!
Excellent idea… Get going with it: http://www.polyfabrics.com/ (or go to China!). Can I have a set for Christmas?