Excellent suggestion. The "Guests are getting lost or stuck" is one of the more annoying messages. As you say, it's a relatively short distance. And if you look at what the guests are thinking, you get the usual "Can't find (insert ride here)". I thought I'd seen or heard somewhere that it was four minutes, like ride times, and graph lengths.
I've found that guests whose action is labeled as heading towards an attraction are willing to walk a maximum of 200 tiles towards an attraction before giving up. This is a relatively short maximum compared to real life. I recall being in Cedar Point, willing to walk from the park entrance to Steel Vengeance. I checked the distance of this walk on Google Earth and it turns out that it is about 5,500 feet.
Increasing the number of tiles guests are willing to walk towards an attraction could make large parks more functional because guests would be more able to intentionally walk across a large park towards an attraction. Maybe double or triple the number of tiles guests are willing to walk towards an attraction and similarly increase the number of tiles guests walk before thinking that they can't find an attraction or the park exit?
For the minimap UI, it's at a scale of very few pixels to the tile, and when looking at the location of guest thoughts it's hard to figure out more then a general region of the park where, for example, paths are dirty, or more importantly where there's a concentration of "I want to go home" from a path accidentally not connecting. Since it already seems every tile has at least one pixel, there's no need for more resolution, but it would be useful to allow "zooming in" on the UI minimap through increasing the number of pixels per tile displayed on the screen. Particularly with guest thoughts it would being able to narrow down the location of problems much more closely would be a help.