here's some ideas and my response to them
7-segment display... no.. not good for letters. and it's a license plate, not an LED
if you used images or shapes or whatever for each character in the vehicle mesh itself, you'd have 36 nodes per letter, and with 7 letters, that's 252... leaving, as I understand it, 3 nodes for everything else. call the cops
could be possible to mount a bot that looks like a letter/number instead
that way it's 36 bot models, and just 4-6ish mount points
this is promising, although to me it means 7 bots.
barnabas uses bots to have more animated doors... bots could also be used for extra meshes in cases like this.
1 bot (with 37 nodes in its mesh) in 7 mount points, with each mount point offset so that the bots perfectly fill in the license plate area.
a person who was willing to do this (not I, despite my recent trend of surprisingly complicated small improvements) would need to be very careful about knowing the width of the license plate and how much to move each mount point