Lack of tessellation was a big one. In many cases you'd rather have the polygons pre-tessellated in the file format. Now you can. Or you can avoid doing that and save the bytes.
The format is also designed to slide onto the GPU more easily. If you're writing a vector map from scratch, I say just do MLT.
There was never any support for more complex geometry. Now someone could add curves.
Attributes had to be fairly simple. Now you could conceivably do hierarchical attributes.
The requirements for navigation data tiles get specific and weird (from a visual perspective). Now it can be added without breaking existing data.
Lack of tessellation was a big one. In many cases you'd rather have the polygons pre-tessellated in the file format. Now you can. Or you can avoid doing that and save the bytes.
The format is also designed to slide onto the GPU more easily. If you're writing a vector map from scratch, I say just do MLT.
There was never any support for more complex geometry. Now someone could add curves.
Attributes had to be fairly simple. Now you could conceivably do hierarchical attributes.
The requirements for navigation data tiles get specific and weird (from a visual perspective). Now it can be added without breaking existing data.