I recall someone already asked why StrokeIt does not have any knowledge about the application where the gesture was drawn.
While your ideas seem to increase StrokeIt usability and add to its features, actually they would degrade performance and kill the goal to keep StrokeIt quick, small, and easy to maintain.
First of all, Jeff would have to make StrokeIt able to detect if there are any selections at all in the window in which the gesture is drawn. And if we are at that level, why restrict it to files? There are many different windows/panels containing objects of many different types, not only files.
And then again, why restrict it to Windows Explorer? I haven't used it in years on my machine, and would not use it even on other computers if I weren't explicitly forced to. There are many others, some of them much better than Explorer, like Total Commander, Directory Opus, etc. possibly each of those using different functions/apis/whatever to achieve their goals with objects selected. You would have to implement an interface to each those and that would mean an enormous and constantly growing collection of functions because everyone would ask why is "replace-with-your-application" not supported?
To go further, what if you selected 3 files/object? And what about selecting 4 or 5 or 6? Or any other arbitrary number? This would create a mess.
Fear not though :) not all is lost. The pro version of StrokeIt is also capable of running Lua scripts besides the built in commands. Lua is a quite powerful script language able to call dlls. If you can get docs for your favorite application (or at least know how to call its functions), you can do whatever you want in it based on whatever you want it to be based on (including the number of the files selected, or even the count of letter 'e' in the selected files, just to give an extreme example). I use it to save the file that is currently played in WinAmp or FooBar to a specific location by drawing gesture 'S' when listening to music while I work. It should not be much harder to figure out how to start a specific program or execute a command based on how many files are selected in Windows Explorer.