A writing system either developed for a language that lacked one before the Modern Ages or meant to transcribe an existent writing system uses the Latin alphabet.¹ A good writing system is, to the extent possible, morphophonemic. To the extent it is phonological (i.e. the letters represent the phonemes represented in the spoken version), letters have the phonological values they have in the IPA. This is important for the following reasons:

1. The IPA symbols were standardized just for the purpose of internatonal use, not only in phonetic transcription, but also for phonological and – to the extent typographically feasible – orthographic representation.
2. In the IPA, letters are assigned the phonological values that they had in Latin. This, again, was done for a number of reasons:
   1. When the Latin alphabet was devised (first millennium BC), there was a maximally simple correspondence between letter and sound.
   2. The phonology of the Latin language is, by typological standards, relatively simple. The vowel system, in particular, is a prime example of symmetry.
   3. All deviations from the Latin model that were produced in the Latin orthographies of more modern languages are complications and deviations from a relatively straightforward system.

This implies, conversely, that the orthography of certain modern languages is not an appropriate model for the writing or transcription of further languages. Deviations from these principles are not seldom observed:

• Orthographies developed for minority languages use Latin letters for sound values they have in the language dominating in the respective society.
• Transcriptions of non-Latin orthographies into the Latin alphabet often use spelling conventions of the language which serves as the metalanguage of the particular transcriber.

This holds, in particular, for English as a metalanguage. The English orthography is, among alphabetic orthographies, the most desperate in the world (closely followed by French orthography). Typical and frequent examples of the use of colonial-language orthography in the writing of minority languages include the following:

• On the English model, /u/ is written as <oo>.
• On the French model, /w/ is written as <ou>.
• On the (Latin-American) Spanish model, /w/ is written as <hu>, and /h/ is spelled as <j>.

Such writings are not advisable for any language (including the “donor” languages). An extreme case of subordination under the orthographic conventions of a locally dominant language is observed in some transcriptions of Classical Maya. The original orthography of the language is logosyllabic. Like in other such cases (e.g. Akkadian), glyphs are transcribed by sequences of Latin letters which correspond to the presumed phonological form of the words represented. Some transcribers (e.g., Law & Stuart 2017) use Spanish spelling conventions in the transcription, representing, e.g., /h/ by <j>, apparently because the dominant language in the geographical area where Classical Maya used to be written is now (i.e. after the language is extinct and no longer written) Spanish. This would appear to be a promising method of posthumously colonizing languages which have so far escaped colonization by an early death.

¹ It is true that some writing systems developed in the Modern Ages use the Arabic or Cyrillic or another alphabet. This is not recommendable on linguistic grounds.

References

Law, Danny & Stuart, David 2017, "CLASSIC MAYAN. An overview of language in ancient hieroglyphic script." Aissen, Judith L. & England, Nora C. & Zavala Maldonado, Roberto (eds.), The Mayan languages. London: Routledge (Routledge Language Family Series); 128-172.