title_body: What symbols should I use for phonemes when I have many vowels?
upvoted_answer: One possibility is to use German-style umlauts, i.e., ü for /y/, ö for /ø/, and ä for /æ/; you can keep the symbol œ for /œ/. I'd recommend against having both ae and œ in the writing system because of confusability. The choice of tilde for nasalisation is a good one, IMO. The most problematic case are the two different kinds of a-sounds, but there are some African languages just going with a and ɑ (and there is also an uppercase letter for the ɑ in Unicode, it is named Latin Alpha). All the symbols are readily available in Unicode and should not pose insurmountable difficulties in text processing.