RCT3 had separate unload stations way back when, and I've always wondered why Planet Coaster devs couldn't seem to accomplish the same thing. There are many examples of coasters where riders get off the ride at a separate station to where they are loaded and it just seems like a common sense way of increasing throughput.
Having dual stations with switch tracks for rides with typically low throughputs due to slow station operations would also be awesome. Probably too technically challenging for he devs though
Themeable freefall-drop-track sections (like on Thirteen, Verbolten and the recently-opened Potter coaster (the latter of which actually has two drop tracks)) would also be a nice addition.