This is just a rough idea I've been spinning through my head, but I was considering  how I'd tackle a particular part.

The main premise is you can construct a variety of vehicles to use in the world, via a series of different parts, in the vain of Space Engineers and Crossout. The focus will be more on 'cool and aesthetic' than totally super realistic, a player would be rewarded for creative design. As such I wanted vehicles to have a variety of propulsion methods such as wheels, tracks, repulsors (hovercraft), hoverjets (VTOL), aerojets (aircraft), etc.  And of course mechanical legs. Realistically legs have numerous issues, and some of these would be unavoidable (legs tend to give you a higher profile for example).

So I hope to get ideas for what would make creating a legged vehicle advantageous and amplify them to make them a valid choice. Maybe if I go over what I consider the advantages/disadvantages of the others.

Wheels: Cheap to produce, vehicles travel reasonably fast, can carry a moderate amount of mass. Easily damaged? Often suffer greater extremes of slow down on difficult terrain.

Tracks: Moderately costly, tough, able to traverse a number of terrain types without great amount of slow down, can carry heavy masses. Slower than the rest.

Repulsors: Ignore most surface terrain, very fast, can cross liquid surfaces. Expensive, trouble going up inclines? Can only carry lighter masses.

Hoverjets: Allow aerial movement, direct vertical movement, fast. Very expensive, can only carry the lightest mass.

Aerojets: Allow aerial movement, fastest vehicle. Very expensive, always in constant motion and requires advanced landing techniques and sufficient flat ground to land, lighter mass.

I think the main advantage of legs is also obstacle traversal, except with even better results. Flat or rough terrain don't make a difference / no penalties.

Also with "gripped" legs you could have full-on climbing capabilities.

Otherwise yes, they're fragile. Depends if you're thinking heavy mech type of legs, or more agile spider type of legs.

Another possible advantage is that the load it can carry shouldn't affect it too much. Think of a robot with 8 legs, moving 2 at a time, while the load rests on the other 6. Only part of movement that would be affected by the load would be moving the body over to the 2 legs that just advanced, which could probably be less than wheeled vehicles, that constantly need to move under the weight.

Depending on your game mechanics, "Jumping" may be a useful feature. 

For your terrain crossing ability with tracked and wheeled vehicles, you may want to include considerations towards the balance between load bearing/ground pressure/obstacle climbing: You can pack many small wheels next to each other to maximize your load capacity and minimize your ground pressure, but it comes at the cost of how large of an object you can naturally climb over. If you go with really BIG wheels, then you can climb over bigger things more easily, but you can't fit as many wheels down the side of a vehicle. 

Also a fun mechanic to play with for your repulser tech: If less weight you put on the craft for a given repulser engine size, the greater the vertical clearance it can still do.

Another mechanic to possibly play with: Turret height. 

Legged units can crouch, or slightly adjust their stance more than other units. (Wheeled and tracked units could be fitted out with 'lift kits' and allow a bit of adjustment, but not much.) This means that you could huddle your legged unit behind a low hill to hide in one instance, and then have it stand on tip-toe basically to shoot over a tallish building in another. The player temporally gives up mobility to gain stealth/hull down positions, but retains the ability to remain flexible at other times.

Third option I can think of: Side stepping

Wheeled and tracked units move based on where the front of their hull is pointed, but nothing says repulser tech and legged units can't readily move side to side to pop in and out of cover. Potentially extremely useful if you include variable armour: While a tracked vehicle could carry loads of amour with ease, a legged unit could focus nearly all of its heavy armour in one direction, and have a better chance of keeping that pointed at the enemy and still move around. The tank would be more likely to have to show its softer side in order to reposition itself.

I think legs definitely will have a terrain movement advantage and be able to traverse steep inclines better than most other vehicles.

The main thought since my post, perhaps not the most realistic, came from where I was deciding on the support of mass of the different types above, I think I'll have legs able to support the heaviest mass with the least amount of movement slow down (Heavy massed vehicles still go slower, but the increment of the slow down is less drastic than on other types of propulsion).

Also I know propulsion isn't a great word, I think I've seen 'motivator' used once.

8 hours ago, allnamestaken said:

 

Repulsors: Ignore most surface terrain, very fast, can cross liquid surfaces. Expensive, trouble going up inclines? Can only carry lighter masses.

Sometimes the lore guides the game, and sometimes the game guides the lore.  When you asked yourself the question "trouble going up inclines?" that should have immediately set of a bell in your mind.  This is an obvious case of where you want to let the game guide the lore.  Whichever way works best for your game, and within the mix of other vehicle types that you have, is how you should make the repulsors work.  Then the game writes the story when you go to explain this in the vehicle/repulsor description, or wherever you wind up explaining why repulsors have trouble going up inclines (or why they are particularly good at it, or whether they can't at all... whatever you wind up going with).  In this case you are free to make it work however works best, and then use how it works to add depth to the lore and maybe it even becomes relevant in a specific story/quest within the game.

The game writes the story and the story designs the game.  Back and forth, endlessly, until someone wearing a suit rips it from your hands and publishes it.

;-)

Have you played Robocraft?  It has a good deal of these locomotion types.  Their hover is a pain to keep stable, easily tipped over, which makes for fragile craft if they take damage.

Turn radius might be a problem too.  Legs can turn in place, wheels, not so much.  Even treads can't really turn in place easily.  

I'm just imagining Gundams with wheels instead of legs lol.

37 minutes ago, Jordan Hoffman said:

I'm just imagining Gundams with wheels instead of legs lol.

It's more goofy to me imagining why someone would put legs or arms on a giant armored vehicle at all =)