What about adding keyboard shortcuts for the other filetype actions which can be defined to each mime type?
Examples for what I mean:
- filetype declarations can have a keyboard shortcut field
OR
- F1 would execute the default action, F2 the second action defined, F3 the third, etc.
OR
- Shift+Enter would execute the second action on a file
I prefer the first one - this way it would be possible to edit filetypes e.g. to pressing enter (or doubleclicking) would display the file, and F4 would call the edit file option, if the type has one.