Firefox isn't AppleScriptable, unfortunately (one of the many reasons I generally don't use it). GUI scripting (i.e., scripting the actual interface actions—button pushes, keyboard strokes, etc., rather than the Apple Events which such actions are the normal front-end to) might be a possibility, but the specifics would depend on how various of your Firefox prefs are configured. Unless, of course, you're willing to make Firefox your default browser, in which case
tell application "Safari"
activate
set theURL to URL of document 1
end tell
open location theURL
should work. However, since this means that clicking links in other apps, which currently open pages in Safari, will now open pages in Firefox instead, I doubt you want to go that route.
As for "a market for it," I suspect that all but the most rabidly mouse-phobic would prefer to do what I do, which is simply to drag and drop the Safari page's favicon on FIrefox's Dock icon.
