Instead, the list should be parsed and each character in the text should be displayed using the first font in the list which is a) available b) has a glyph for that character
Interesting. I doubt that Inkscape will ever implement the correct behavior as it would require that Inkscape be able to do all the book keeping to know which characters are available in which font. At the moment we use Pango to come up with the best match for a given font specification. Getting Inkscape to use the first available font in the list will be a small step forward (right now it treats a font list as a single font name and thus won't match anything).
I'm not sure if this is completely related to this discussion, but I'd like to leave my 2 cents. Currently inkscape does a rather weird font substitution (at least I, as a user, can't tell how and when it works) and there's no clear indicator of that substitution except the warning icon in the font selector once the text element is edited. In my experience (both with libre and proprietary applications) automatic font fallback has never been completely succesful and frequently it's more problematic than helpful. Manual selection of the replacement is always annoying but at least less dangerous. To make it worse, there's no visual indication that fonts have been replaced in Inkscape, so things can look fine at a first glance when in reality they are very wrong when you sent the artwork to print, exported, etc. Automatic font fallback can be useful for document accessibility, but from a graphic designer perspective it's too dangerous to be considered as a viable option. Since I consider Inkscape a design application I'd say it's more important to actually KNOW that the original font isn't available than finding a quick replacement (which potentially could completely destroy the original design because the character set isn't complete, metrics don't match or simply its style is different). IMO the ideal solution would be the use of embeddable fonts as it was stated before, but meanwhile a safer choice would be to replace the missing fonts using the default (or yes, using some font replacement technique) but making it visually clear the the fonts used in the document aren't the originally assigned, using some highlight or visual cue of some kind. But anyway, before speaking about how fonts have to be replaced, Bug #168658 should be addressed since it's too dangerous for artwork integrity.