The use of ieung (ᄋ) to show accentuation is really innovative.
Thanks, I didn't wanted to leave the graphical accent out of the writing system because I think it is somehow important even though it can be elided and understood easily. And since there is no final ng in Spanish and it is visually quite beautiful (at least for my taste xD) is used ᄋ.
there's an odd mix of phonemic and orthographic principles at work.
I'm aware of it, I have an explanation for some of the choices, but some other choices are just arbitrary.
Why have separate symbols for v and x, for instance, but not q and j?
I chose it like that because, in general, people who write more or less well in Spanish tend to use the differenciation between b and v for etymological reasons. As for x, I've never seen "eksistir" or "ecsistir" instead of "existir". However, it is really quite normal to read things such as "ke" instead of "que"(you know, in personal writings, msn and so on.) On the other hand, the etymology wasn't applied completely to the rules for the use of g and j, for example you write "coger" but, "usted coja" and "digo", but "dije" (I know it is because of the sound, but still). It made me think that the difference between b and v is more important for etymology than the use of g and j, so I tried a more phonetic approach for this matter.
Why have any silent consonant at all, particularly when it would've been useful to reuse hieut (ᄒ) for /x/ or /f/?
Just for the same reason above, since I already had j/g ([x] sound) written as ᄏ, and f written as ᄑ, I could use ᄒ to represent the silent h, which is useful to distinguish, for example, "haber" and "a ver" (하벷/아 프헻).
에이 요 탐볜 이세 우나 아닾타숀 델 한굴 파자 엘 엣팒옿 훗토 뎃퓃 케 엔텐디 커모 푼쇼나바...
I think yours is quite straightforward but still I think there are some things that could be confused. For instance, you wrote "español" as "엣팒옿" and "funcionaba" as "푼쇼나바" but then ᄑ is used for p and f. BTW, I think the ñ is really perfectly represented, but I just didn't know how to write that jamo o_O.
Besides, I think it is quite important to indicate the difference between c/z and s for a Spaniard, because even though there are some zones of seseo and ceceo, we are very used to our standard dialect which clearly distinguishes the two sounds.