Luca and Asura seem like obvious ones to me -- they're based on real things, people, or relatively real names, while the other options aren't. I can't really see anything but those as being the 'intended' names. Although we ended up with "Marth" as official, so what do I know?
Chitose's name is more annoying. I mean, "Chitose Charma" seems like it was most likely the intention (especially if she's a spellcaster or whatever) but it also sounds stupid
in English. Chitose Cxarma is unpronounceable, but it has some charm to it... is the absurdity of her name actually something people comment on in dialog? If so, I'd say go for that, even if it's unpronouncable. As long as you don't use "Thitose" it should be fine (that one sounds more like a character from Beath of Flams
As for the original names, some of those are better than Ilia at least. And ルカ is the most common name in RPGs, so I tried not to romanize it in a way not used by Final Fantasy 4, Chrono Trigger, Suikoden 2 (this one used Luca,) or any of the others I'm sure I'm missing.
The thing is, with names like those (especially taken in the context of their last names, and the other names in the list), it is obvious that Chitose notwithstanding they intended for most of the characters to have what they saw as relatively normal-sounding "Western" names. Ilia/Iria, Spada, Ange, Matthius, and Ricardo are all fairly common Western European names. 'Luca' fits perfectly into this list. (And Chitose is at least a common real-world name.) "Ruca" doesn't fit at all, since it's not a common real name; if it was used, he'd be the only person in the cast with a relative nonsense word for his first name. "Ruka" is a real name, but it doesn't fit his last name or with the majority of the cast.
Sure, you could romanize it both ways, but that doesn't mean both options are right
. I think the context makes it clear in this case which one was intended; "Milda" is a European name; so is Luca. "Ruka" definitely isn't, so "Ruka Milda" makes very little sense. And "Ruca", of course, doesn't even seem to be a name at all -- it's a Mexican-Spanish slang term for an old maid. When you have the option between translating a name as an actual name or as something else, I would say naturally you should translate it as a name...
Yes, it's a common name in RPGs, but so what? The character has a common name; he's supposed
to have the same name as all of the other characters you mentioned, and, who knows, maybe it was even a sly dig at one of those characters (not likely, but not impossible either.) Sure, if you don't want him to have the same name as anyone else because it bothers you while playing, then change his name to something totally unrelated to what it was before when the game lets you name him -- but I think, for a translation, having it closer
to those names would be better, because that accurately translates the fact that it is the exact same name.
Of course, excessive accuracy to what was intended is not necessarily the most important consideration, particularly for something like that, but the general European flavor of most of those names doesn't seem like an accident to me, and it should probably be preserved in the translation; "Luca" achieves that goal, while "Ruca" or "Ruka" doesn't.
I also think that "Ruca" looks stupid. It's just harder to make an argument for that.
"Ilia" and "Iria" are both real names. "Ilia" is somewhat ethnic-Jewish, although not exclusively Jewish.
You might try looking the names up on baby name lists, to see where they're from and what they mean (and to see if they're real names or not.) That might give you hints towards the 'intended' name, if you care. For instance, "Iria" is of British origin, from "Iris" (does the character have any connection to flowers? Is her mother/child/sibling named Iris? Etc.) "Ilia" means "The Lord is my god" in Hebrew (and would be an appropriate name for a staff chick
or whatever, I suppose.) "Luca" is Latin for "Light", explaining its popularity for main characters and heroic people... Presumably its use in Suikoden II was ironic, if they knew its meaning at all. (Not impossible; there are baby name sites in Japanese too, presumably. And you'd hope they put at least enough thought into naming major characters to look them up in something like that, at least to see that their names don't mean something stupid.)
Anyway, you probably wouldn't turn anything up with a search like that, but occasionally it could reveal, say, a linked meaning with another character's name that the translation should preserve, or something like that.