Please, please do not let the tab key have anything to do with the functionality of v2. The tab key is terrible for any kind of navigation and it really annoys me that software uses for anything other than creating tabs in text files. The problem is that you have to cycle through items in a fixed order and to cycle backwards you must hold down shift and then press tab which is awkward and annoying. Any moving between potentially multiple text boxes should be done with the arrow keys.
Also, aside from being unnecessary, I think that the idea of multiple text boxes undermines the visual simplicity of FARR.
OK so after criticising your ideas let me be a little productive and contribute one of my own.
In the case of finding a file/shortcut and running it: v2 should behave exactly as it does now.
In the case of finding a file and performing a different action on it, in ADDITION to being able to type the action followed by the file (or however you choose to make the syntax work)...
...how about searching for the file in the normal way, selecting it by cursor keys, and then typing the action you want to perform on it. As a keypress other than enter is detected another text box pops up to the right of the item and searches for actions relevant to the file type similarly to the way that the main text box searches for files.
While all this is being done, perhaps the main text box could be automatically updated to reflect the action that the user is attempting in such a way that if you had typed it's contents into the main text box originally and pressed enter then exactly the same action would have been performed on exactly the same file.
User types "mp3 dylan" into main text box
10 results displayed
User keys down to the fourth one (4.mp3) and types play
By now the main text box has automatically changed it's contents to "play mp3 4.mp3" (or whatever you decide is best)
User presses enter. Action is performed
The entry in the history is "play mp3 4.mp3"
Perhaps some visual cue could exist to let users know that when they select an item they can type an action.
The advantage of this approach is that it guides users through the process of performing more complicated actions on files but also shows them how they could've saved time by typing the action and searching for the file at the same time in the main text box.