Would definitely like to see where you get those characters (Conquest, Marquee, Journey Guide, Galactic Legend, etc) 

Curious where you think their power level is or where you'd like to see them

I’d gladly take these, especially the Old Republic era characters, and Sith Stalker Starkiller. I just like a lot of the legends content.

For Jawa, I'd like to see the Jawa Warlord Wittin who in Legends controlled with remote a Trade Federation STAP with B1 Droid to fight in Jabba's Demolition Games. Wittin could have good synergy with the STAP if in a party and he'd also be the first Dark Side Jawa in the game and aligned with the Hutt Cartel.
https://starwars.fandom.com/wiki/Wittin/Legends
https://starwars.fandom.com/wiki/Wittin

For Imperial Remnant, I'd like to see the Reborn Shadowtrooper. In Legends, these Stormtrooper variants were Dark Jedi hybrids in cortosis armor. Originally non-force-sensitive humans, they were artificially made force-sensitive by the Empire Reborn through power from the Valley of the Jedi and further enhanced with Artusian crystals embedded in their armor. Their armor also provided them cloaking abilities.
https://starwars.fandom.com/wiki/Shadowtrooper

501st: CC-1119 "Appo", Light Side, Support, 501st, Clone Trooper. Obtain in Marquee

Bad Batch: Crosshair, Light Side, Attacker, Clone Trooper, Bad Batch. Obtain in Journey

Bounty Hunter: Todo 360, Dark Side, Support, Droid, Bounty Hunter. Obtain in Marquee

Clone Trooper: CC-3636 "Wolffe", Light Side, Tank, Leader, Clone Trooper, 501st. Obtain in Marquee

Droid: AP-5, Light Side, Support, Droid, Rebel. Obtain in Marquee

Empire:  Rick the Door Technician, Dark Side, Tank, Imperial Trooper, Empire. Galactic Legend, or at the very least Journey

Ewok: Peekpa, Light Side, Support, Ewok. Obtain in Marquee

First Order: Commander Pyre, Dark Side, Attacker, First Order. Obtain in Marquee

Galactic Republic: Gregor Typho, Light Side, Attacker, Galactic Republic. Obtain in Marquee

Geonosian: Geonosian Queen (though I really like your idea of the Geonosian Zombie), Dark Side, Support, Leader, Geonosian. Obtain in Journey

Gungan: Rish Loo, Light Side, Support, Gungan. Obtain in Marquee

Hutt Cartel: Muchi, Dark Side, Tank, Hutt Cartel. Obtain in Conquest

Imperial Remnant:  Brendol Hux, Dark Side, Attacker, Leader, Imperial Remnant. Obtain in Marquee

Imperial Trooper: Jumptrooper (jetpack trooper), Dark Side, Attacker, Imperial Trooper, Empire. Obtain in Marquee

Inquisitorius: Inquisitor Barriss, Dark Side, Healer, Inquisitorius, Empire. Obtain in Conquest.

Jawa: Teeka, Light Side, Healer, Jawa. Obtain in Marquee

Jedi: Mortis Ahsoka (possessed), Light Side, Attacker, Jedi, Galactic Republic

Mandalorian: Satine, Light Side, Healer, Galactic Republic, Mandalorian. Obtain in Journey

Mercenary: 4-LOM, Dark Side, Attacker, Bounty Hunter, Droid, Mercenary. Obtain in Marquee

Nightsister:  I'd give Savage a NS tag since he was enhanced by their powers

Old Republic: Dagan Gera, Light Side, Tank, Old Republic, Jedi. Obtain in Journey

Phoenix: Kallus, Light Side, Attacker, Leader, Phoenix, Rebel. Obtain in Journey

Rebel: Stormtrooper Luke, Light Side, Attacker, Rebel. Obtain in Marquee

Rebel Fighter: Maarva Andor, Light Side, Support, Rebel, Rebel Fighter. Obtain in Marquee

Resistance: Jannah, Light Side, Attacker, Leader, Resistance. Obtain in Marquee

Rogue One: Tivik, Light Side, Support, Rogue One, Rebel, Rebel Fighter. Obtain in Marquee

Scoundrel: Maz Kanata, Light Side, Support. Obtain in LS RotE planet special mission

Separatist: Sniper Droideka, Dark Side, Attacker, Galactic Republic, Separatist, Droid. Obtain in Marquee

Sith: Pong Krell, Dark Side, Tank, Sith, Galactic Republic. Obtain in Conquest

Sith Empire: Tenebrae, Dark Side, Tank, Sith Empire, Sith. Galactic Legend

Smuggler: DJ (Benecio del Toro's character from Last Jedi), Dark Side, Support, Mercenary, Smuggler, First Order, Scoundrel. Obtain in Marquee

Tusken: Krayt Baiter (unsure of actual name or "job" of the tuskens who volunteered for this or if they're just normal raiders, and unsure of the leader's name who interacted with Cobb/Mando), Dark Side, Tank, Tusken. Obtain in Marquee

Unaligned Force User: Smilo Ren (Qimir, from the Acolyte), Dark Side, Tank, UaFU. Obtain in DS planet RotE special mission

Wookie: Gungi, Light Side, Attacker, Wookiee, Jedi. Obtain in Marquee

Old Republic: GALACTIC LEGEND Grand Master Satele Shan

If I were to make my own picks, I think these would be the ones.

501st: Jesse (Marquee)

Bad Batch: Crosshair (Marquee)

Bounty Hunter: Calo Nord (Marquee)

Clone Trooper: Boss (Elite Marquee) (with Scorch, Fixer, and Sev to follow after him as regular Marquee characters)

Droid: HK-50 (maybe a large character with three of them like the great mothers to reference their battle on Telos IV, or a regular character that has a mechanic similar to Dark Trooper, and B1 where you need to beat it multiple times to truly defeat it) (Marquee)

Empire: IT-O Interrogator Droid (Marquee)

Ewok: Treek (Marquee)

First Order: BB-9E (Marquee, or Elite Marquee)

Galactic Republic: Adi Gallia (Marquee)

Geonosian: Gizor Dellso (Marquee)

Gungan: Kleef (Marquee)

Hutt Cartel: Bib Fortuna (he could maybe be an Elite Marquee character at best to make a second Hutt Cartel team with)

Imperial Remnant: Incinerator Trooper (Marquee)

Imperial Trooper: Phase Zero Dark Trooper (the clone veteran turned mostly cyborg with the ARC Caster from 2005 Battlefront 2)  (Marquee)

Inquisitor: Purge Trooper (Marquee)

Jawa: Blizz (Light Side Jawa Bounty Hunter from the Old Republic MMO) (Marquee)

Jedi: Mara Jade Skywalker (Journey, Legacy, or Legendary)

Mandalorian: Mandalore the Preserver (aka Canderous as Mandalore) (Marquee)

Mercenary: Migs Mayfeld (Marquee)

Night Sister: Mother Zalem (I’m not huge on the night sisters and this one seemed interesting when I looked her up) (either Marquee, or Legacy event maybe?)

Old Republic: Satele Shan (Conquest)

Phoenix: Alexsandr Kallus (Fulcrum) (Marquee)

Rebel: Bail Organa (Marquee)

Rebel Fighter: Old man Gregor (Marquee)

Resistance: Old man Lando (Marquee)

Rogue One: Galen Urso (what other options even are there?) (Marquee)

Scoundrel: Cobb Vanth (Marquee)

Separatist: General Kalani (Legendary, or Elite Marquee)

Sith: Darth Phobos (Marquee, or Legacy Event)

Sith Empire: Darth Marr (Marquee, Elite Marquee, or Conquest)

Smuggler: Dryden Voss (dark side smuggler) (Epic Confrontation, or Elite Marquee)

Tusken: Darth Krayt (Legacy Event)

Unaligned Force User: The Ronin (Dark Side Unaligned Force User from the Star Wars Visions series) (Marquee)

Wookiee: Hanharr (Old Republic era Dark Side Wookiee Bounty Hunter) (Marquee)