Lets get this game working first.

Privateer's greed would undue the war dec nerf...

The gas nade is a terrible idea

If you're trying to suggest this would be optional content, that isn't how you operate an MMO. Besides, CCP already said that this game will always have free expansions just like EVE Online. You never have to pay for new content releases in CCP games.

Gas grenades to damage armour doesn't make any sense to me.

Our suits are sealed environments, we're meant to be able to function normally in our Dropsuits on worlds where there's no breathable atmosphere. The only threat with hull breaches in space is the risk of being sucked out with the air or accidentally turned into a makeshift plug sealing the hole closed. And gas should affect us exactly the same way a non-breathable atmosphere would. Which is to say, it means nothing.

A chaff grenade that disrupts sensors would be nice to have as a sort of smoke grenade, but a gas grenade dealing damage is a silly idea.

Also, even without the sealed system, why would lack of oxygen damage your armour anyway? You know we have a (ridiculously tiny to the point of nonexistent) health bar beneath the armour, right? It's not displayed, but it's there. It's probably less than 10 HP worth, but it exists. You can be stripped down to 0 shield and 0 armour and keep fighting.

I can see the logic in having damage applied - first to shields, then armour - if you're trapped against a breach in a ship's hull. If it wasn't so improbable as to be almost impossible, I'd possibly see the value in gas grenades and Oxygen deprivation affecting a DUST Merc when they're at precisely 0 armour but still have health. Because of the almost complete lack of those scenarios, however, I don't see a real need for it.

Splitting the player base based on who's purchased a particular DLC and who hasn't probably isn't a good idea at all. Everyone should always be playing together to keep the queues as short as possible.

Making a game mode that totally excludes vehicles, orbital stuff, installations, and anything that isn't infantry running down corridors or whatever is also probably not a good idea.

I think doing space ship related stuff is fine, but it's maybe a better idea to incorporate really large ships which can actually fit vehicles in them and keep a lot of the same elements at play in typical games. You don't want to make a DLC that only appeals to one section of the player base -- the people who like playing infantry in close quarters.

As a pve mission, boarding ships could be possible. Like recover something from a rogue drone infested freighter then blow the reactors to take out the drones.

To many issues with boarding player piloted ships.

The EvE expansions were always free and mandatory. Once it was released the game could not be played till it was installed.

Pve content could be setup as a separate free download, so people that just want to pvp could skip the download time and hdd space.

The hacking module would probably be the electronic breach, a specialized sticky re for doors would be nice.

Most npc ships don't have capsuleers(immortal pilots), they have human crews, npc ship boarding as a pve could be interesting.
EvE missions also have a lot of structures on asteroids and towed structures that could be in the suggested mode.

You didn't use the word "free" to describe this. The vast majority of DLC is paid-for. What CCP does for EVE is irrelevant. This isn't EVE. If they've said all future stuff is free, great, but I haven't read that.

The whole point is that people who would consider themselves vehicle drivers, or anything but close range infantry players, would derive nothing out of this. What's the point in putting together a big, complex DLC game mode if the majority of players wouldn't even want to play it? Having major content patches be exclusionary to anyone but people running around with an AR/shotgun/mass driver/HMG probably isn't such a sensible way for them to spend their time.