DW3, now, would be interesting, but I've no clue how you'd manage a DW3 character in the dungeon unless you just do Sage.
Re Dragon Warrior 3: Well, Sage from the get-go seems like a bad idea to me, it's impossible to have happen in-game. Probably it'd be better just to give the option of either Wizard->Sage or Pilgrim->Sage, the general combinations used with the Book of Sartori. Still some playership issues, but at least people who've played one DQ game will have some idea of what the characters can do. Definitely should be mapped out first, I'd think... I'd assume the class change to Sage would be at Floor 4, and also temporarily screw up their stats due to going back to level 1? Seems doable. Wizard & Pilgrim are both worth about the same amount; Pilgrim's healing and buffs are always handy, while the Wizard is fast (always good in the Dungeon) and gets an ID weapon on floor 2 for breaking up stalls despite being really frail. Sage is obviously just awesome, though being below average speed means he's only so good in the Dungeon.
Anyway, two random ideas for the Dungeon, one semi-obscure and the other not so much. Something a bit annoying about Marcus & Athos, the two most blatant "help my back-loaded team get through floors 1-3," is that they actively suck more and more as the floors advance due to the magic of DL scaling. It's not even that they don't get any new abilities and fall behind as the floors get tougher, it's that they become actively statistically weaker too. It'd be nice to have more characters who can help early, and while they might not be great later on, they don't tail off as much. And people with revival early are surprisingly rare. Hence...
Red XIII (w/ Materia) (Simple version)
Red starts out with the Fire materia attached to All (as in game). On Floor 2, he gets the Revive, Ice, and Lightning Materias.
* Floor 1: Fire
* Floor 2: Fire2, Ice, Bolt, Life
* Floor 3: Ice2, Bolt2
* Floor 4: Element3 spells
* Floor 5: Life2
Pros: Early reviver. Very nice magic damage early, hits a number of elements. Limits are a nice disincentive to attack him. Above-average speed.
Cons: The magic becomes so-so by Floor 5 and is actively meh by Floor 7, making Red a fighter. Limited Moon means that spending his MP hurts his damage. Can't MT his non-Fire damage and MTing Fire hurts effectiveness.
Red isn't great on later floors, but he's still a full-reviver with some cool limits, so he's hardly dead-weight. 2.0 points, maybe? Those magic spells HURT on Floors 2-4, and having - according to the stat topic - 109% average speed is pretty useful for getting the drop on people.
Alternately:
Red XIII (complex, Cloud-lite version):
Red starts with the Fire materia attached to All on Floor 1. Every floor afterward, choose one more materia from the following list: Ice / Lightning / Revive / Heal / HP-Plus / MP-Plus. Red's materia have on each floor AP equal to (insert a chart, so 3000 AP on floor 2, 50000 AP on floor 5, etc. - basically "a reasonable amount of AP for this floor if playing through the game normally and leveling this materia).
This version gets status healing and HP / MP buffing too (Don't laugh at the MP buffing, remember the Limited Moon). Presumably after floor 7, when all those materia had been picked, he'd rely on the special late floor bonuses instead. Seems like a 2.5 to me? The lack of MT and healing means that competing choices like Garnet or DQ4 Hero still have a lot of appeal.
(EDIT: Forgot Red's starting All materia. Knew he had something other than just the Fire.)
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And for a more obscure idea... since Yuri1 and Yuri2 already are in the dungeon... perhaps the option for the Ziggy1 / Ziggy3 team?
Ziggy (Xenosaga III)
Pros: Heat. Fantastic defense, magic defense, and HP. Heat. Keeps boost from battle-to-battle, so might be able to speed himself up in later fights. Aside from special attacks, great break damage offers a way around stallers. As a character, stock went up in XS3 where others have gone down. Even gets Offensive late for team buffing. Heat.
Cons: Below average speed. Some bosses in XS3 immune Heat, so bit of an interpretation question on its effectiveness. Doesn't block many statuses for most of the Dungeon.
Ziggy's pretty cool - everyone's seen the wondrous brokenness of pre-nerf Firefly now, and Heat does the same thing. This is balanced by Ziggy needing to waste his first turn using Heat, and him being slow. He also Doesn't Die, which makes Heat work great with him. Damage is fine too, if not broken or anything. There's also a pretty cute combo for fights after the first one in a Dungeon - since XS3 boost is like FF7 limits, and stays from battle to battle, Ziggy can boost in after a very fast party member and use Heat early in the round after all. Pretty cute.
Only problems I see is that XS3 playership is a bit low, and that there's two kinda tricky interpretation questions. One, in some battles a team with Ziggy will want to leave one person alive, stall, and let Ziggy build up tons of boost for later battles. People often times forget about this strategy, and moreover, normally irrelevant questions of targeting come to light - do you let bosses attack themselves, for example? Since the strategy for the Dungeon in such situations would often be to just quickly commit suicide, if allowed, which would prevent Ziggy from farming boost. The other interp problem is what I mentioned above about Heat - it works on MOST bosses on the game, but not all. Fully status-immune bosses are more common in other RPGs, though (even though Heat is technically Ziggy's own status?), so does it work there? Uh, tricky question. (This would be the advantage of Viking Luneth for a Firefly-replacement - I believe that his Provoke works perfectly on everything. I know I read a strategy online about defeating FF3DS's superboss via Provoke abuse with a Double-Shield Viking.)
Tentatively, I'd say 2.5 points. He'd be 3.0 easily if his Heat could be guaranteed to work in all situations.