In the dark ages (when the only way to know what other "exotic" type designers were doing was call people, get some names, then call those, ad continuum - something I never did) I designed my own keyboard layouts for Armenian, Arabic, Hebrew, Cyrillic, Vietnamese, and who knows what else. Assuming there really is no standard* you can go about this in one of two ways: either shoot for making novices comfortable, or making professionals efficient. The former involves mapping the letters to the closest equivalents on the Qwerty keyboard. This is not as hopeless as it seems, even for something like Arabic (or Jawi). The advantage of a phonetic mapping is quick and pleasant pickup by all users. This is what I did for Armenian in the 80s** since back then people -especially Armenians- were still afraid of computers to begin with; even today it helps gentle souls get in on the game. In contrast the latter approach involves making typing efficient*** by arranging the letters very thoughtfully according to frequency and frequency of sequence (like putting "t" and "h" so that you can type them quickly, not putting much where the left pinkie is, etc.). This is of course a lot more work, and because it requires much more memorization from the get-go it causes a lot of people to complain, and some people to give up. The good news is that these days you can do both, and give each user a choice.

* And if there is, assuming it's not a disaster.

** This layout I made ended up in Windows XP, although I'm still trying to get at least a credit for that... I'll be making some determined moves towards that end at this year's ATypI conference.

*** Although we know what happened to the Dvorak keyboard... :-/

hhp

I guess it all depends on what user you have in mind, in the short term, mid term and long term.
If you have a long term user in mind, go for the most logical, fast and complete layout for the language. It will not become popular anytime soon but it is the right thing to do.
For the short and mid term, particularly if the user familiar with English keyboard layout is in mind, and someone who does not use the layout full time, a phonetic mapping on QWERTY English is more practical.
We made a QWERTY Persian keyboard layout for Mac which was an instant hit among Iranian Mac users, almost all of them residing abroad. But for the use of a nation, efficiency and completeness should take the priority.
Persian has a government standard based on keyboard layout used on MS platform which itself is a derivative of MS Arabic layout. So I don't have to be worried about the Persian standard.
btw thanks hrant for the info. Now I know who to blame for this awful awful Persian standard :-)

Actually my Arabic/Farsi layout was a very niche thing (it was made for video titling on the Amiga, although some people did use it for typesetting small ads in a yellow pages), so it was nothing even close to a standard. The nice thing about it though was that it was completely "typable" - no need for any keyboard software whatsoever. It's my Armenian layout that's in Windows. BTW, could somebody please show me what Armenian layout(s) MacOS uses these days?

hhp

Riccardo just sent the MacOS keyboard XML files, and guess what: they're also using my keyboard. No crediting, nothing. The problem with Apple is, they have an even "better" deaf ear than MS... Is anybody from Apple going to Mexico City?

hhp

Salam, kawan. Can I have your contact/ email? I would like to introduce someone who might be a help to you for this project.