Which mechanics do you want and which not?

Interesting topic. I'm looking forwards to seeing everyone's lists. Anyway, mine are below. None are deal breakers for me if they are/aren't in, and I've probably listed some stuff that is known from leaks etc that I've just not noticed.

Yes

• Server browser for core modes (seperate one for Portal).
• Keyboard and mouse support on console. 
• The fortification system from BFV (I just liked it lol).
• 3D spotting and good visibility. 
• 64 player matches.
• Supply stations on flags for infantry. 
• An official Hardcore mode (I don't like Hardcore personally, but think that people who do deserve a dedicated mode). 
• Night maps. 
• Solo/Coop mode.
• Appropriate cosmetics and weapon skins. 
• Naval warfare.

No

• Forced crossplay.
• Attrition system for infantry. 
• Temporarily/Rotating game modes. 
• Squirrel suits and Spiderman grappling hooks. 

ElliotLH​ Naval warfare, good one!👍🏻 Night maps too, if done properly. I’m talking Nivelle Nights and Prise de Tahure type of night maps, not the poor attempt of making El Alamein into a night map in BF2042.

1. Seven classes from BF2
2. Squads from BF2
3. Field Commander from BF2
4. Destructible & repairable Commander assets on attackable home HQs
5. Destructible and repairable map installations such as bridges from BF2
6. Commo & Tactical rose from BF2
7. Strategic map and Commander map from BF2
8. Platoons, server browser, custom settings for servers and Battlelog

All of these and game would be dream come true. 😎

Yes

• Server browser 
• Official hardcore mode 
• 64 players in the game
• I agree, the BFV fortification system should return 
• Being able to rent servers 
• That tanks and planes have the gameplay they had in BF3
• Locked weapon system, similar to BF4 would be nice and quite balanced
• Cooperative mode (like in BF3) 
• Naval warfare
• Atmosphere similar to BF1 
• Dynamic climate 
• That team play and the return of battlelog be encouraged more 
• Crossplay option between consoles

No

• Forced Crossplay
• Portal 
• Gun play BF2042/BFV 
• Skin without meaning and horrifying colors without a war theme. 

Yep, that's exactly what I'm hoping for with night maps RanzigeRidder2​. I reckon there's a good chance because of that clip in the reveal. 

So BF2 then? 

It was a great game, but you could always just play BF2?

Would like:

• Semi-auto weapons that can compete with full-auto (not at all engagement ranges, obviously, but with a Venn diagram-like overlap. The guns in BFV were, generally, pretty good for this. 
• Weapons that feel punchy without a TTK that's too low.
• Input-based matchmaking.
• Unlocks and upgrades that don't require you no-life it. I have a wife, family and career to attend to. Games should be fun.
• A clear and easily comprehensible upgrade system. No forcing players into gamemodes they don't care for to upgrade their weapons.
• The ability to teamkill with call-ins. In BF2, there was no more satisfying feeling than dropping a jeep on a sniper camping in the home team's uncap.
• Rental servers with proper admin controls. The modern cheating problem basically stems from publishers wanting to control the full stack for monetisation purposes. If there are to be time-limited skins and other rewards for engaging in the way the devs/publisher wants, such as completing tasks on official servers, so be it; I'll do that if I want the reward. If I just want to play the game with a community, then let me do that. BF4 had some great servers with rule sets that led to really interesting games. One of my favourites was a server that implemented rules as close to BF2 as possible: Friendly fire on, squad leader only spawn on, regen off, 100% health, 100% damage. It made players slow down and take a more considered approach. I had a Portal server with those rules, but yeah... Portal. 
• Related to the above - Portal: Either take it seriously and use that in place of a rental server program while giving us the tools from the get-go, or just give us a rental server program. There are very good reasons for previous iterations of the game being so sticky. Admin control was, IMO, the most important. 
• Rob Smee. More of the world needs to know what a male Tracer looks like. 

Would prefer to avoid: 

• SBMM. Not every match needs to be a sweat-fest. Sometimes joining a server and your team getting royally stomped can be fun, as can joining a server and carrying the noobs to victory. 
• Crossplay on by default. It was game-breaking in 2042. Please don't do that to me again. The lag gives me flashbacks just thinking about it now.
• Specialists. Give me traits I can apply to my soliders instead.
• Extreme traits. Some of the specialists' "features" in 2042 were gamebreaking. No physics-defying wingsuits, please. Mckay should be paraplegic given the G-forces his lower back endured. 
• Lag, desync and zergs. Only one 2042 map (Orbital) really worked as a 128-player map, and that was because it was effectively two maps that players had to decide to move between. For the rest of the maps, it was too much - everything everywhere all at once, or maps that felt empty. 
• Vehicle spam. I get it - combined arms is part of the DNA of the franchise. I have more than 40,000 tank kills in BF3. Vehicles are usually amazing in Battlefield, except for 2042, which was basically "infantry farming simulator." Please get the balance right.

I don't have a PC neither I don't like MnK as input device. 

Input-based matchmaking would solve most concerns around KBM on console.

It keeps things fair by grouping players by their control method. That way, controller players aren’t thrown against KBM users unless they choose to.

This makes KBM support a win-win,  more player choice, balanced cross-play, and a better experience for everyone.

Yes:

• 64/32 players in the game (32 for CQB maps, i like maps from Battlefield 3: Close Quarters )
• Weapon Unlocks system like BF3 or BF4
• Voice chat like BF2
•  2 Large maps with a focus on vehicular combat (for example BF 3:Armored Kill)

No:

• Hazard Zone mode
• Cringe Soldier Voice Lines (i mean - like BF 2042)