Do any of you have any knowledge of how Arabic script has been adapted to
African languages?

I have a question from someone who wants to know how they should write
prenasalization and more than 3 vowels in Arabic script. Below is an
excerpt from his message to me.

If you have any knowledge of other languages that have coped with these
issues, or perhaps some resources where some of these issues are discussed,
I would be grateful for the input.

TIA,

Bob

<excerpt>
We would like to write in Arabic script, but found the characters
furnished by Unicode slightly awkward: They provide plenty of
variations for some characters, sometimes even overload them with dots
and things (like for kaf), but no variation whatsoever for others
(like mim). And especially, I couldn't find possibilities for vowels
(we need e and o [in addition to a u i], both long and short). Our biggest
problems besides the vowels are to find a possibility to represent mb
(prenasalized b) and ny (palatal nasal).

Our folks would like to avoid combinations of consonants (like mim and
ba following each other to represent mb) as well as "re-"using
unneeded characters of Standard Arabic (as that would necessitate
re-learning when the person wants to make the transition from reading
the mother tongue to Standard Arabic).

So what we would really like is a mim with a dot underneath for mb and
something like possibly a nun with a little v above for ny. The
problem with the latter though is that we also look at the little v
above a consonant to represent the short e (and the little hat above
for the short o, the prolonged forms with ya and waw respectively).
</excerpt>