I realized after I thought back on the DLC BTB map Avalanche that the mancannon between the shotgun and the laser is in between two open expanses of snow. These areas seperate each team's sniper hill and power drain mancannon from the rocket hill and camo/bubble/bruteshot- the distance was so vast that it prevented players from walking across it, practically dividing it for infantry. Even if one was at the sniper spawn and the keyhole was clogged, it would be safer to go to the base, teleporter and then rocket mancannon to reach the invis or ghost/laser area because of warthogs. This snow expanse has no equipment, weapons, cover, high ground, or objectives, so what purpose does the abyss in between the center indoor mancannons, as well as the snow on either side, serve? They had to have added one or the other first, and I don't think that they would have wanted such a plain, empty man-cannon room for nothing. If they took away the abyss and the adjacent outside sections, the room could have been smaller and designed a bit differently, with a continuous floor, of course. The extra snow made room for more vehicle combat, but otherwise vehicle combat would have occurred closer to the middle of the map, where there is plenty of space. I loved avalanche, but I think that this change would have improved map flow and made the map less awkward for infantry. I also wonder if the designers were aware of how completely they would bottleneck players through the single, small keyhole entrance. An opening adjacent to each keyhole leading into each side of the mancannon room would have completely solved that problem, would it not? Then even three players on each side wouldn't be afraid to advance through one or both of their openings and duel it out, instead of creating a boring impasse by creating a wall of potential fire and grenades. Did the designers want to encourage flanking through the laser side of the mancannon? Even that would just gain the shotgun room itself, and this is assuming that players would intentionally make the decision to travel that far; only the suggested 2nd doorway would allow crossfire on the sniper/overshield hill. One last problem with a simple solution would be the teleporters- did the designers assume that players wouldn't bother camping behind their own base teleporter? Did they want to encourage attacking the base from two directions? Two receiver nodes and one sender node per destination would look more complicated, but it would become just as easy to remember. Each destination, by the design of the existing teleporter sytem, would have a 50% chance of being the actual destination of the traveler, making camping for assassinations useless.
Avalanche was one of the few maps I thought worked well with teleporters because both areas were almost always controlled by the same team so there were no orientation issues. I know most people were afraid to walk out in the open areas, but I did it all the time and rarely had any trouble.
First of all, know (if you don't already) that Avalanche was a remake/semi-reimagining of the old CE map Sidewinder. So in part that already answers your question: they were re-doing a map that was the way it was, and they weren't going to change it drastically in a manner such as scaling the entire map down (although there are some substantial differences between the two). Second, what people loved about Sidewinder and Avalanche both is that they're true BTB maps with lots and lots of room for vehicle play. Sidewinder was the biggest map in CE, with the horseshoe shaped playing field almost like two Blood Gulches converging at one end. Avalanche was built the same way; all the snow is for driving around on. One reason I think the design of Avalanche is fairly smart, and an upgrade over Sidewinder, is all the shortcuts built in specifically for infantry in case you don't have a vehicle handy. Sidewinder had the teleporters (also a two-way joining one side to the other - replaced by mancannons to the middle on Avalanche, which IMO is an improvement). The mancannons in and out of the base weren't on Sidewinder either and work very well for quickly moving between a couple of important positions, as well as attacking objectives. Most crucially, that middle mancannon lets infantry traverse a huge chunk of the map length-wise while staying mostly out of harm's way with respect to vehicles - but with the risk of having to enter the keyhole, the map's most powerful and contested position. I assume they were quite aware of it. It takes a five second glance at an overhead view of the map to notice that design. I assume they did want to encourage flanking, and the dual active camos at the bottom of the horseshoe enable you to flank the keyhole room from below, or just bypass it and go around the other way on foot, hopefully without being spotted by a warthog or hornet. I did that many a time in CTF and assault games. I don't think your change would be a bad one, but I don't think the established design is bad either. Warring for the keyhole was a big part of playing that map - I actually looked forward to it. Any teleporter, two-way or otherwise, invites camping - same with lifts. That is what it is. This problem was worse in CE; they made changes to teleporter functionality and how they built the nodes into the levels to cut down on this by Halo 3. Regarding your proposed change, competitive players would gripe endlessly. Deliberately introducing randomness is not a solution to that type of player. One thing that might work is for them to add some kind of "phasing in" effect when you exit a teleporter - a period of maybe a second where you can move around but can't interact with anything, or be interacted upon. It would let players exit a teleporter and orient themselves/check their surroundings safely, and if someone was camping, the fight would start on even footing (give or take a power weapon). I don't know if I've ever seen that proposed but it seems like it might work.
Nutduster, thanks for the answer- I didn't play multiplayer when I had CE. I see what you mean about the active camos, but they spawn once every three minutes for one person. As you said, it wouldn't be good if a hog saw you on foot when walking around to their side. As for the teleporters, two receiver nodes would suit that base design well- remember how it was in a nook in the corner, and there seemed to be a symmetrical one on the other side of the base, except that was actually a thin incline leading down to the bottom of the base? Well, the other receiver node could be at that end, and the sender could be in the middle. This way, the only way that a player could be screwed by the randomness is if they were staring straight at one or the other. If they were waiting at the flag stand, they wouldn't be surprised, they would simply adjust their aim 40 or so degrees. It would simply prevent assassinations, not defending the base from enemies on the other side of the teleporter. The same goes for the rocket hill, if both were in the corners of that constructed hall-cave. One would simply have to stand back if they were to wait. Your solution would be confusing if it was map specific, and if it was universal, it might be appropriate for every situation, as in a mini-game, because the traveler couldn't shoot immediately. I'm guessing you're saying 0% damage done and taken for a couple of seconds, right? How would they know when it's done? It just seems like it would be a lot harder to get used to for players that might not be exposed to it often.
It would be throughout the whole game, I'm thinking. Putting it on just one map makes no sense, and anyway, the teleporter-camping issue is universal; it's happened on basically every map with a teleporter since Halo CE. To make it work there would have to be some visual indicator, like the player being partly see-through or flashing or something. You're correct about the camos only applying to one person at a time, but fundamentally this is a vehicle map - if more than a couple members of your team are hoofing it around the entire horseshoe, you're doing it wrong. Avalanche had a lot of warthogs and mongooses (plus hornets, a ghost, choppers, banshees, and tanks - depending on which gametype you played); it was never intended to be primarily for foot traffic. Arguably it was the most vehicle-intensive map in all the Halo games along with Sandtrap.