quoting Serafín, 農, Canada:

Suggested romanization:

/pʼ pʰ b tʼ tʰ d tʃʼ  tʃʰ dʒ kʼ kʰ ɡ qʼ qʰ/ <p' p b t' t d c' c j k' k g q' q>
/f θ ð s ʃ x ħ ʕ h/ <f þ ð s S x H 3 h>
/w j/ <w y>
/m n ŋ/ <m n N>
/r/ <r>

The use of <H> is from Klingon and Arabic, <3> /ʕ/ is from Kabyle ɛ and Arabic, <N> is sometimes used for /ŋ/ when romanizing languages from India. Regarding /ʃ/ <S>... do we allow /sh/ to happen at all? If we don't we could simply use <sh>. I can type ŝ or ś or š easily, but I think of our mates on Windows 10...

I'm really not a fan of using capital letters with distinct meanings in romanization, and I think that in the year of the lord 2018 we can expect people to figure out how to type characters outside of the ASCII range, regardless of OS. I suggest:

/pʼ pʰ b tʼ tʰ d tʃʼ  tʃʰ dʒ kʼ kʰ ɡ qʼ qʰ/ <p' p b t' t d c' c j k' k g q' q>
/f θ ð s ʃ x ħ ʕ h/ <f þ ð s š x ħ ɛ h>
/w j/ <w y>
/m n ŋ/ <m n ŋ>
/r/ <r>

I'm fine with the vowel system changes