One strong preference I have is to stop having a must-merge lane on highway entry. I feel this creates many dangerous moves and resulting accidents as people ramp up to highway speed and then, sometimes have no where to go and are running out of room.
I'd prefer to see the entry lane from one interchange, become the exit lane for the next. That way there is much less pressure to merge, and generally, you have at least 2km to get into an ongoing travel lane.
I would then like to see most interchanges designed so that the highway exit ramp is on the near-side (better sightlines), comes to a traffic lit intersection with the road to which one is exiting (better safety for pedestrians and cyclists than slip lanes); and the entry point is on the far side, so, if for whatever reason, you were were unsuccessful in merging, forgot, or got off at the wrong exit, there's at least one lane that passes through the intersection to allow you to re-enter the highway almost immediately.
I do agree, additionally, the highway, should transition down in size at logical points (after a major exit, where there is a net drop in traffic); and by and large, should transition down slowly, dropping one lane after each additional exit, not a rapid drop that creates multiple, frequent merging movements.