From my searching it doesn't seem possible without rooting the phone and then knowing exactly where to poke around (which doesn't seem easy to come by either).
Even if I was to write an app that messed with the vibrate service offered by the OS, it just lets me control my own app's enabling or disabling of a vibration and doesn't appear to have a way to control it through a global configuration.
I also looked for other means of doing it, like seeing if there were Power profiles that could be tweaked (since some services like wifi and vibrate are prohibited when the battery level gets too low) but couldn't find anything on that either.
I know some people have submitted enhancement requests / wishlists to the android folks on this already, seems you're not alone. Good luck.