Locked Weapons should be the default.

This was a very poor decision and should have never been implemented. It's just placating to whatever is popular, but goes against the very core of the franchise. If you let whatever is popular dictate how the game is built, the whole thing would quickly become a samey bore with zero bite. The whole point of having designated weapons is to challenge the player, and they want to be challenged even if they don't know it. You go around giving everyone exactly what they want, then what's even the point of having any challenge at all; may as well just let players do whatever they want. Walk though walls, shoot rockets out of their SMGs, "who cares it's popular."

No. you people are making a Battlefield game, that means you make a BATTLEFIELD game, not some designed by popular demand shlock with no identity. 

Recon at the back can spot and mark targets and will benefit from a scoped rifle.

Engineers are in and around vehicles and need to stay on the move and benefit from high fire rate and fast reloading SMGs

Assault is at the tip of the spear and benefits from high damage mid capacity rifles

Support are backing up the battlelines with supplies and benefits from large capacity LMGs so they can stay in the fight between reviving teammates

Guns determine the class. It makes sense and it's worked before. There's no reason to change it. Unlocked just makes the games samey and boring and makes having a class system at all mostly pointless.

Say you want to snipe from a nice perch you found on a hillside, you're doing great, but you keep running out of ammo. In the unlocked mode, this scenario would be solved by the player simply equipping a rifle to the support class, dropping a supply box and just sniping the whole match endlessly.

Now same scenario in locked mode: You now have limited rounds, and you're aware of this, so you're choosing your targets carefully and locking in so every shot counts, so now there's an intensity to the match and you feel the pressure. Then you're out and you either need call a squad mate in to drop you a supply or go find a support teammate for ammo, then return to your perch. Making the players move, creating breathing room in the battle and promoting player movement thereby increasing the chance of encounters.

See, unlocked mode is doing several things wrong. It's creating one-man-armies, stagnating the battlefield and killing squad/team play. Things that Battlefield is known for. In the locked scenario, the player is being forced to move and adapt to the situation, not just sit there and interact with no one. The reason weapon locked classes is so important is because it makes the battlefield come to life, it makes team play matter, it promotes squad dynamics, it makes spotting and identifying an enemy's class matter so you know what to expect and can navigate that challenge appropriately. It makes the encounters far more interesting and prevents every game just being bunch of different classes all running just ARs and shotguns.

Open mode should be relegated to an option in Portal, it shouldn't even be in the official playlist at all. You want to bring in new players but you guys aren't even willing to introduce them to something new. what's the point of it??