Hangul (Korean) script for languages other than Korean

A long time ago, I attempted to apply Hangul to
various languages, at least English. I called it Segul
(world-writing), as opposed to Hangul
(Korean-writing), but I also simply called it Sejong
after the Chosun king who invented it.

Now that I'm currently on "vacation" here in
Washington, DC, and have a lot of time on my hands, I
took on that project again. I'm trying to apply the
principles to (at first) the Big Six languages
(Eng-Spa-Rus-Arab-Hind-Mand) Of course Sejong did
design his alphabetic-syllabic script for Chinese as
well as Korean, including modifications of the
characters for the alveolar, retroflex and palatal
sibilants.

For the non-Chinese languages, I want to be able to
write them in Hangul the way Sejong himself would've
done it. My biggest problem is how to represent /r/
(there's one letter for the phoneme represented by
allophones [r] and [l]).

I've seen a German translation of _Hunmin chong-um_
(Sejong's treatise on Hangul), but it was so long ago,
and I don't even think it's online anymore. Is there
an online translation anywhere now, preferably in
English, or should I just go to a good university
library (or the LOC here in Washington)?