As much as this could be a very intriguing project, I personally think that one of the highlights of the Vectrex is the true vector-based graphics. Using LCD/LED would take away most of the magic and turn it into a basic "emulation" type of unit. However... I wouldn't mind seeing a modernized version with color vector graphics and a larger display. That could open a whole plethora of options for the homebrew community. I also love the 3D imager, so utilizing that in a modernized way would be a bonus.
But don't give up the search. It took me almost 20 years to get mine and its one of the highlights of my game collection!