standard orthography for multi-dialectal language

[MDbaloch]

Dear all,
What should be the criteria for the standard orthography of multi-dialectal languages ?
count the broadness or the  originality of a specific dialect ?
Thank you all !

[MalFet]

What is the purpose of the orthography?

[MDbaloch]

What is the purpose of the orthography?

Design single (standard) orthography for all dialects of a language to unified the whole community.

[MalFet]

Beyond that, I mean...

Is there another nearby orthography that this orthography should be compatible/incompatible with? How much phonological diversity is there within the dialect pool, and is the goal to standardize oraintain variation? What other orthographies do the speakers of this language know, and how much time and effort can you expect them to put into learning a new one? In what contexts will this orthography be  used?

[MDbaloch]

Beyond that, I mean...

Is there another nearby orthography that this orthography should be compatible/incompatible with?
yes, there is.
How much phonological diversity is there within the dialect pool, and is the goal to standardize oraintain variation?
Dialect A               Dialect B
Phoneme                Allophone

[t̪]                              [θ]̹
[ɡ]                              [ɣ]
[d̪]                              [ð]
[p]                              [f]

Now, the dialect A doesn't have these Allophones in its phoneme inventory.
but the dialect B has all A's phonemes in its phoneme inventory.

yes, the goal is to standardize oraintain variation .

What other orthographies do the speakers of this language know,

English,Persian

 and how much time and effort can you expect them to put into learning a new one?

just a few days !

 In what contexts will this orthography be  used?

need more explanation

[MalFet]

Dialect B has both the obstruents (/tgdp/) and the fricatives (/θɣðf/)? Contrastively?

[MDbaloch]

Dialect B has both the obstruents (/tgdp/) and the fricatives (/θɣðf/)? Contrastively?

yes, but these fricatives (allophones) are borrowing sounds of neighbor languages.
the pure phonemes of the language are the obstruents.
on the other hand Dialect A doesn't have these fricatives at all !

[MalFet]

So if they're allophones, they're not contrastive phonemes. That makes things simpler, though. The idea that a dialect would sometimes spirantize its stops is very familiar.

If that's the extent of variation between dialects, I'm not sure what you're asking exactly, since producing an orthography seems to be a relatively straightforward issue of choosing glyphs that will be easiest for people to use. Most orthographies don't represent allophones anyway.