[Warframe Mod Slots]

Is it plugged in?  Your reactor, that is.  I agree, you forgot to buy a bag of potatoes at the store.

[Essential Mods for Weapons]

I'd like to see a greater range of dual-stats, as a way of mixing and matching additional effects without forcing everyone to go cold turkey on their DPS.  Like now we have Chilling Reload for cold+reload, but it's only for shotguns.  I'm all for the full gamut of element+weapon QoL combos for all weapon types, since most of the time the QoL mods have to go pound sand to make room for damage and god knows some weapons would feel a lot better to use with those bonuses.  I'd also like to see a class of elemental mods that have a "doesn't combine with other elemental damage" effect, so that you can get base element damage types alongside secondaries they'd otherwise combine into.  Something else that could be cool would be an exilus mod that removes the movement speed penalty while shooting.

[2 FA is not working in the game]

Might be a stretch, but Mixer is a Microsoft service, and Warframe's 2FA has generally failed to work with MS stuff(such as people with live.com, outlook.com, or hotmail.com emails).

[Exilus Weapon Slot]

I've been thinking the exact same thing.  There are a lot of QoL weapon mods we "can't" use due to needing the slots for other whatsits.  Max ammo, magazine size, beam range, reload speed, etc.  Or maybe rather than have an exilus slot, start rolling these effects into a whole new pile of dual mods.