Wow, that's a lot of good advice. I'll try messing with the framerate options! (Once I can talk them into looking at the screen again. Last time, after less than 20 minutes of trying to embark, they spent the next day-and-a-half recovering from the headache. It was scary.) Thanks!
In your ideal world, what would DF look like?
There's a limit to how much I can change. I could blend temporally adjacent frames, but I'm not convinced motion-blur is the desired effect here.
The way it was described to me, it sounds like blurring frames might do it. The sudden jarring transitions will still happen even with a lowered framerate, but if the blurring is across enough frames to produce a smoothed transition effect, that could be enough. Even if you're rendering at 30+ FPS and simulating at 60 FPS, the actual number of on-screen visual game events is usually not more then 3-4/second. You'd have to tune it for the rate at which the interface blinks, so maybe blur the past 5-10 frames? It's hard to say without seeing it.
In addition to the transparency options above, I'd suggest a micro-sized, non-blinking overlay on a tile to indicate that there's more than one character to be displayed. Typically it's either an overlay (like Depot view) which might even be more usable if you just put a red or green icon in the corner of a tile, or a fairly clear-cut case of a primary icon with an icon of secondary importance being alternated. (A dwarf carrying an object or an object on a ramp.) A perfect-world implementation of a 'picture-in-picture' approach would expand the various contents of a tile when you mouse over it.