What I have been working on - A work in progress.

Is there only one route across the Canyon?

 

While the bridge appears to be quite the well thought-out central structure, I would recommend adding at least one other route across the canyon to prevent any camping issues. I wouldn't make it something quick like a man-cannon or a straight shot across, but another way to transverse the canyon would be optimal. Maybe two small side-bridges, one on either side of the main bridge. If you want to encourage players to us the main bridge by making it more open or accessible or faster then that's fine, but I wouldn't suggest leaving it as the only way to get across.

Take a look at most official maps with a bridge or bridge-like connection between two halves of the map--Narrows comes to mind immediately of course, but you could also take a ForgeWorld example and look at The Cage--there's always an alternative to the most obvious route across. How fun would Narrows have been if you didn't have the ability to man-cannon across and get behind the enemy? Not as much fun, for sure.

Also, while the bridge may be the central structure, you still have decent chunks of land at each base, so adding in side-bridges would allow the rest of the land available to the player to have some sort of usefulness other than "run from here to get to bridge."

 

You absolutely need an alternate means of travel. Everything else is secondary at this point. If you run out of credits necessary to put weapons down on top of adding other routes, you need to reorganize and delete trivial items.

Designing a map around a bottleneck is fine as long as there are other means of relieving the pressure in the center. Mancannons across, teleporters (though not advisable) are fine, as used in Narrows from Halo 3. The map will be stagnant and relatively unused if you don't encourage movement. You want the players to feel they can sweep around the backside and kill their opponents, not a head-on rush every single time on a standard map.

 

I agree on the second route of crossing....my suggestion would be an upper walkway which is accessible by grav lift....if you do a walkway lower than the bridge it'll be too each to kill from above. If you do the upper walkway it will give people a chance to get a flag back across it in a more protected route.

 

My general rule of thumb is at least three ways to go anywhere, and the bigger the map (and the bigger the hypothetical team size) then the more important that becomes. This looks like a good-sized map so I'd suggest at least two alternate routes. Think about Narrows, which this compares to for obvious reasons - the main route was the bridge, but you could also go under the bridge or man-cannon off to the side. Three primary ways of getting from base to base. I'd suggest the same here - you could copy the Narrows man cannon concept, and/or add one or two walkways above or below (or to the side of, if somewhat sheltered) the bridge. I don't really like the idea of a teleporter though, because it looks like the distance you have to cover is an important part of the map design, and being able to skip that instantly and while completely avoiding fire (unlike with man cannons) would probably compromise the map too much.

 

There's different ways you could approach it. You do want to account for travel time - don't make any one route too fast or easy. Perhaps you could put a floating platform under or above the bridge at the halfway point, with a man cannon to it on each side, and man cannons off of it as well? So basically a person would have to make one jump, traverse a small platform, and then make another jump, and they'd be exposed to fire (depending how much cover you put on the platform and how elevated it is) for some or all of that time. You could do almost like a mini-bridge crossing above or below the regular one, and they can man cannon in on one end and then back out on the other. And you could even have access (stairs or a ramp) from the main bridge to this second bridge, giving your players more options for moving around.

edit - here's the kindergarten overhead view:

 

I would advise an option similar to megapwn's up there, but I would also advise a third option, one that shouldn't bankrupt you. I would say, along with the man cannons, make a straight-shot bridge at either end of the canyon, which is completely covered by one of the tinned pieces (apologies, can't remember the name right now), or, for better coverage, the brace tunnels. One of these set on whichever side of the map (I'm thinking the side closest to the ocean) would add intersting gameplay dynamics couples with the man cannons up there:

1) Players can take the bridge, and there are the number of options for them there
2) Players can man-cannon across, but are subject to people shooting them during their two airborne journies
3) Players can attempt the covered walkway

The covered walkway would be both a blessing and a curse--while off the beaten path, the covered walkway would offer full protection from the chaos potentially going down at the bridge and, if the other team is not paying attention, would offer a straight-shot into their base. On the other hand, you're essentially in a giant tube, and there's no way out--if you find 3/4 of the way through hat they're waiting for you on the other end, you could be pretty well screwed, unless you can fight your way out of t. For that reason, bringing a flag down there would be a risky venture, while simply using it to run across the canyon would not be as bad.

If you ask me, you add in the man cannons and the side tunnel, and you've got the workings of a really fun map.

 

I look forward to it!

 

Good to hear. My concern has been echoed by everyone else here. It's fine line between endless CTF stalemate and un-opposed capping.

 

you should put cannon mans in the back of each buildings so you can move swiftly and flank the others

 

That still creates a choke point in the middle, and snipers have a direct view of this from either side of the map. In this situation, whichever team has the best sniper is almost guaranteed victory. Since you've already ditched the idea of giving your bases depth, and thus made mancannons a bad idea for objective games, you have two options: build another bridge, or make your bases taller so players have to get up some kind of tower to grab the flag and the time to get the flag is increased enough to allow mancannons. There's also the problem of cover for the bases. It's not so bad for the base with a few trees to block sight lines, but the other base has absolutely no cover. Heaven for snipers, hell for anyone else.