Planned (objects, not text.. can't see how that would work well) since the start.
I'd love to be able to feature text like "SWAT", "FBI", and so on, onto vehicles when I'm a cop. I'm sure crews would love to do the same to their vehicles. This would obviously be open to abuse, but I don't see any reason why the existing word filter for number plates can't be used for text too.
Where I have seen this feature on another server, there have been some really creative ways of using text on vehicles such as making spoilers and sunstrips by using careful placement of symbols. It'd be really cool to see what people would come up with if you changed your mind about this.