Idea:
I believe that there should be a percentage chance for a vehicle or group of vehicles that's off-road capable (i.e. tracked vehicles mostly, or simply vehicles that aren't an LCV or HLT) to decide to go off-road when heading to an objective instead of just following roads.
Vehicles should also assume a different formation (such as wedge, line, column, diamond, etc) when going off-road.
Pros:
The benefits of this would be that low-intensity gameplay is no longer repeating the same old "fly along this road, fire a few missiles and rearm", as you would have to more actively scout for units that are possibly flanking. There are quite a few avenues of approach, particularly on the eastern side of the archipelago.
Vehicles who would otherwise be sniped by stationary MBTs or aircraft on the main route might find some protection when traveling undetected through forests or hilly areas.
Offroad movement would also be a more realistic approach to ground command in general, as it wouldn't make sense to be putting all of your units on the same road that keeps getting bombed.
If vehicles were to move along the coasts more often or otherwise in less-expected areas, we could see a higher usage of Darkreaches and Chicanes to patrol the outer areas. With the new PAB-250 Darkreach loadout, it's even more feasible to target those pesky off-road groups who are flanking along the side, as they would have minimal air defense with them.
Ships could also play a greater role in coastal defense if some units were to sneak along the beach.
Cons:
Players might be annoyed if their base is suddenly being camped/destroyed by a group of enemy vehicles who basically appeared out of nowhere... However, this risk encourages patrolling/defensive gameplay.
It's understandable to assume that this would also create more lag as vehicles need to pathfind - the solution would be to make more predefined offroad 'roads' to choose from: one is randomly used when going offroad.
Cheers