So, since some additional FEA characters were being discussed.... to sidetrack for a bit, I think some of the FE characters might be a tad overcosted at the moment. This is because "ST damage" with no healing or tricks (read: Not Elincia / Moulder) is a niche most teams typically only need 1 of, perhaps 2 at most. It doesn't matter how dodgy or countery they are (short of Firefly), the enemies will likely ignore them until the revivers are down, and it's fairly unlikely these characters can solo (short of an early Athos type situation) if it isn't the final fight.
So, just to note again... knocking Knight to 1.0 is actually potentially okay, but if so, it's because "ST damage" is a niche that a team shouldn't normally need very much of. Knight is way more unkillable than Lyn or Ephraim, but also gets healing + random RUSE / INVS tricks that might help in stally matches, gets some status blocking & elemental hosing, and also consistently beats down without fear of getting doubled by random speedster bosses. Elf's topic has Knight at .58 PCHP damage; Lyn might be grabbing ~.80 PCHP when she doubles, but she's also much more killable or statusable, especially by ITE. And she'd cost double Knight if Knight is at 1.0 while she's at 2.0. Eph has crazy weakness hitting + OHKO when he doubles, but it's more frequent that he runs into opponents he doesn't double. SO2 Claude, if he gets dinged to 1.5, is a similar case but with even more consistent ST damage and some status blocking.
Basically, I'm suggesting that if Knight & Claude get the discount, give it to the other non-healy characters, too. So Eph->2.0, Lyn->1.5, Marcus/Titania->1.0. Marisa seems a little dangerous to knock to 0.5, though, that's a lot of damage for nearly nothin'. Same with FF1 Monk.
Moving back to FEA... Robin/ the Avatar seems the most obvious inclusion, although it's a slightly dicey pricing proposition - feels like Robin makes a few characters feel silly at 1.0 (lol Marisa / Lute), but is not a very inspiring pick at 1.5. Pick a gender & an asset / flaw (protip: take SPD, it's even more important in the Dungeon than the DL) and go nuts. Notably, since one of the things that makes Robin & Morgan unique is their perfect class access, go nuts with that, too. I'd also assume for Dungeon purposes that Robin supports their entire team, as in-game, and that Robin can be presumed to be standing next to one character of the player's choice (which means they also both get zapped by area-of-effect, of course) for support bonuses for both of 'em (+10 Hit, +10 Avo, +10 Crit, +10 Crit dodge at A-rank).
F1: Tactician, Veteran
F2: Solidarity (+10 Crit / Crit dodge for adjacent allies in addition to the above)
F3: Master Seal to Grandmaster OR Second Seal & L1 off-class ability
F4: L5 ability (Ignis if stayed Grandmaster), L10 + L5 if Second Seal'd above.
F5:
F6: L15 ability
F7: Second Seal if desired + L1/L10/L5 ability of switched class. (also Brave Weapons / Waste legal)
F8+: Just pick any 5 non-DLC skills you want & a class to be in.
Also, an obvious potential postgame bonus would be MORGAN if there's anyone marrigable in your party, though chat with Neph on costing for his or her setup. Could be fun since Morgan could "inherit" totally wacky skills like Red Zone or Night Sword. A very reasonable and weak other bonus for F8 (arguably it should happen without any need for a specific aftergame bonus at all) would be to allow the non-storebought but still moderately plentiful equipment like Celica's Gale, Fortify staves, Levin Swords, etc.
Sample: F-Robin, +SPD / -LCK, Second Seal to Peg Knight on F3 and get Speed +2, Master Seal to Dark Flier on F4 (Relief + uh RALLY MOVEMENT), collect Galeforce on F6, SS to whatever on F7 (Dark mage + Sorc for Hex/Anathema/Vengeance?).
Off the top of my head, Dark Flier, Sage, & Sorcerer seem the money options. DF eventually grabs Galeforce, is fast, and hits both defenses. Sage is if you want to have some kind of Lute variant, Tomefaire + healing. Sorcerer is actually a weirdly team-player type, because he or she goes and stands next to the dodgy dudes to stack -25 Avoid on 'em, is hard to kill if Nosferatu is equipped, and can bust heads with Ruin (and on F7+, Waste).
Thoughts on the above as a 1.5?