For what it's worth, here is my ideal OLM:
Part 1: The Overland
I love maps that let you get somewhere a bit quicker, with the added chance of random variety. I think that to truly meet our goal of spanding Faerun without making tedious amounts of areas, we need something like an OLM. Furthermore, as T-Ice puts it, it's kind of weird that there are just the same few caves in an entire region.
Ideally the OLM does not have to even span a nation. You can have an OLM for a city, a forest, etc. However, using them in such a manner somewhat diminishes the experience of exploring, and should generally be avoided save for huge cities or areas.
Part 2: Travel on the OLM
With the player reduced on a large abstraction of a region, you can make some fun decisions based on
where they walk. Then they are walking over a city (without actually wanting to AT into it), you should slow them down, since they have to go around buildings and the like. When they are on flat, even ground, perhaps they may even get a small speed boost. Going through a swamp or thick forest, however? Well, that'll make your trip take longer. Additional factors such as weather and visibility can also modify this speed.
Part 3: Areas on the OLM
There should be two types of areas on the OLM: static and dynamic. Static areas would be your High Holds, your Rivermoots, your Meteor Lakes, your Winter's Edges. These can have an AT over them to be accessed.
However, with area instancing you can do some pretty cool things with
dynamic areas. You can have a host of generic areas -- generic caves, beaches, forests, roads, etc. Then you can draw triggers representing chunks of areas on the OLM. When the user votes to get off the road or triggers an encounter, the area ID in the trigger is looked for. If it can't be found, it searches for the ID of the generic template to use, and makes a copy of that. You can design 3 or 4 road areas, then lay them out as 20 different encounter areas along one road. This keeps the persistence of a PW, but also makes it so not everyone crosses the same 20 meters of road at the same time.
You can do some similar things with almost any type of area: caves, forests, swamps, etc.
Part 4: Encounters on the OLM
Similarly to movement, some areas are just more dangerous than others. Traveling on the road should always be pretty safe, but there's always the chance of bandits or what have you. Take that shortcut near Wendover to get to Rivermoot faster, however, and you may just find yourself cuddling a hungry ghoul more often. Other factors such as weather and time of day can go into adjusting the encounters.
Part 5: Getting Lost
Another fun thing about an OLM could be getting lost. Akin to a random encounter chance, if you're going through a forest you may end up losing yourself, making your travel take longer. When you get lost, you'll be dropped into that location's area (or area instance), ideally in the middle, and you will need to get to the edge of the map (going to any spawns along the way). When you leave, you won't be exactly where you started.
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All of these ideas stem from the opinion that an OLM should not restrict movement, but rather make traveling on the OLM interesting. You need to plan your course, think of day/night, weather, what types of monsters canonically lurk in which regions, etc. So long as the OLM is also made to be purdy, they should be just as -- if not more fun -- than linked areas. The nature of even the dynamic content being persistent allows people to learn it, too, and go around poking off the road to see what type of content is where. Want to go exploring? Step off the road, enter a forest, then click the "exit OLM" button to be met with a generic mountainous area that could have entirely different spawns than its cousins.
