Good idea.

At work with my newer card, a setting of 1 or 2 on any simple model runs a smooth as glass, but at home a 15 would drag a bit.

When you talk about a possible automatic setting, I see it as a default "high" setting by the user, like 25 - when the viewpoint or objects are being moved.
Then as you sit at idle with a still model, an off-screen rendering of some type would creep in. It could be done in a way where it feels seamless.
Imagine an ultra-slick movement that subtly cleans itself up to where the edges are ultra smooth. But if would have to detect when you instantly need to change the view, so there is no lag.

Google SketchUp does a simplistic version of this by substituting boxes when you are moving the view on complex geometry. Kinda gross.
But I know that MoI has them all beat already. :-)

BTW, a thought I had that could be employed sooner - A simple timing check when loading a file. If MoI has taken more than a user set amount of time, like 30 seconds, then MoI would up the mesh angle or higher then reload the image.
- Could be a simple way, if not through a warning dialog, to let the user know that a monster is trying to open and the mesh angle is set too low.

...Just a few random thoughts about it...