DISCLAIMER: TF2 and Overwatch are the only other character-based shooters I've played, so Paladins, Rainbow Six: Siege, Lawbreakers, etc., aren't gonna be on here.
Before I started making this discussion, I was actually making a discussion about how Dirty Bomb's mercs' personalities are too similar, and how games like TF2 and Overwatch do "character contrast" better (and they do, let's be honest). However, while I was writing it, I actually started to think about how the merc's do still have pretty different personalities. Just looking at the Engineer class, Fletcher is egotistical and arrogant, Bushwhacker is crude and scrappy, Proxy is energetic and hyperactive, and Turtle is easy-going and laid-back. In the Medic class, Sawbonez is a smooth-talker with a side of maniacal, Sparks is both mysterious and adorable, Phoenix is a bit off-kilter but also arrogant, Aura is apathetic and serious, and Guardian is just incredibly annoying. I'm not gonna go on with the rest of the classes, but you get the point. However, SD could definitely do some things to help distinguish the mercs even more.
A thing that Overwatch does, and TF2 does a bit, is display character through first-person animation. While the heroes in the game all have unique weapons, so displaying personality is a lot easier to do for each characters since they don't have to worry about it looking wrong for other characters, TF2 has a few classes that share weapons that still have different animations for them. While all of the classes who can use the stock Shotgun hold it the same, when inspecting it, the Heavy holds the Shotgun with one hand while the others inspect it with two. It's pretty subtle, but it conveys the strength that Heavy has over the other classes. The Scout holds the stock Pistol with two hands and reloads it with an unorthodox and immature animation, while the Engineer holds it with one hand and reloads it like a normal freakin' person.
I know that it would be more difficult to do this for the mercs of Dirty Bomb, since so many mercs share weapons as well as hold multiple different weapons. However, most of the mercs have unique weapons/deployables/devices that should be able to be inspected. If they could be inspected, they should be inspected with some personality. For example, Fletcher could spin the sticky bomb on his finger or toss it around in his hands to display his cockiness and overconfidence. Nader could spin the barrel of the Grenade Launcher and maybe even sort of caress one of the shells (I know that sounds weird), to show how fascinated and in love she is with the Grenade Launcher. Fragger could accidentally pull the pin on his frag and panic about it, and quickly toss it away (hell it could be a funny taunt kill if they ever included those). Phoenix could spin and play with the shape of the Healing Pulse, or transform it into an apple or something.
I know that Dirty Bomb isn't a very "emote-y" game, it would just slow the game down and wouldn't really make any sense. However, they could include First-Person Emotes that you could do while moving and could be cancelled at any moment. Skyhammer could pull out a beer glass out of nowhere, and chug it. Bushwhacker could light a cigarette with some kind of fancy lighter. Sawbonez could pull out three scalpels and hold them between his fingers and have a chuckle. Phantom could bring out a slice of pizza and just shove it into his mask. Aimee could pull out a fashion magazine and kind of do a little gasp and shove it away. Turtle could hold out his robo-arm and have it kind of just glitch and spaz out, on purpose obviously. I could go on with all of the ideas I've got for First-Person Emotes, but I think you get the point.
Although emotes/taunts are something I don't think should be even doable in game, I think something that could help display personality is victory poses. It's not exactly an original idea, and I honestly have a feeling SD is working on something like this, we can all agree that it's a little drab at the end of a CMM match and just seeing a lineup of mercs just... standing there. Not only do I think the CMM lineup should only include mercs on the winning team, because people who lost should not be celebrated (yeah I said it), but those mercs should do more than just... stand there. It's boring, its repetitive, and it just looks bad. So being able to equip victory poses to mercs, even if its just "casual", "confident", and "hyped", its better than just... standing there.
While most of this is just "Cool things Muddy would like to see in the game," it also would be there to serve a purpose. When Dirty Bomb has such interesting characters, and prides itself on them almost more than the gameplay at times, you would think they would want to make them look... well interesting. These emotes, even if subtle even if 99% of players don't even use them, that 1% of players who likes the way they look and truly care about the lore and characters would appreciate it. When a noob player looks at Dirty Bomb and see someone like Stoker, they need to be able to see that he's not pyromaniacal burn-burn man, but a classy gentleman who drinks tea. And you can't just do that with voicelines.