The personal name mode exists mainly because of RR. RR does not assimilate syllables in given names (e.g. 한복남 is "Han Boknam", not "Han Bongnam"). So whenever something is considered a given name, assimilation should be blocked in RR (and the personal name mode takes care of this).
For the surname 나, I want to show "Na" for RR but "Ra" for MR.
RR is not automatically South Korean and MR is not automatically North Korean (in fact, MR is based on the Seoul dialect at the time). Also, showing "Na" in RR and "Ra" in MR for the same Hangul spelling would be confusing to readers.
In addition, this cannot always be automatically done. The surname 임 in South Korean can either be 임 or 림 in North Korean, depending on the Hanja (林 is originally 림, but 任 is originally 임).
If you want to show both the South and North Korean forms, use two different Hangul spellings: one for South Korean (나XX) and the other for North Korean (라XX).
Why couldn't you use a single symbol for all unpredictable pronunciations?
Do you plan to support the Yale romanization system?
Not at present. Implementing it would need additional symbols. Yale requires some inputs that RR and MR do not. Some requirements include:
Long vowels
Reading before the application of 두음 법칙
Representing unpredictable tensification differently depending on the part of speech (e.g. 인기 [인끼] (noun) inqki, 남다 [남ː따] (verb) nām.ta)
Do you plan to implement North Korea's official romanization system?
Not at present. The system has features that make automatic conversion difficult. These include:
Different pronunciation rules (e.g. 넓다 – [널따] in South Korean, [넙따] in North Korean): The authors of this module are not familiar with North Korean pronunciation rules. There does not seem to be an authoritative online dictionary published by North Korea either.
Given names are rendered differently by their origin (non-Sino-Korean names have joined syllables, and Sino-Korean names have spaces between syllables). It is difficult to reliably determine, both automatically and even manually, which names are Sino-Korean and which are not.
I get "N/A" for romanizations.
"N/A" is output whenever the input contains a Hangul character not supported by the romanization systems.
If you get "N/A" when the input contains a middle dot, that is because you are actually using U+318DㆍHANGUL LETTER ARAEA. For a middle dot, use U+00B7·MIDDLE DOT instead.