Start small, and use compromises. Don't try to be completely phonetic, which won't work for the reasons you mentioned.

You can start by undoing misguided spelling reforms of the past. "Debt" used to be spelled "det" but due to incorrectly inferred etymology it was changed to be non-phonetic. There are many words like these.

Then look for major inconsistencies where a cluster of letters is pronounced more than one way, and simplify one of them. For example, "ough" is pronounced as in "tough" more often than as in "though". Change "tough" to be spelled as "tuff" and "rough" as "ruff".

Going further, embrace text/informal writing and use tho, altho, nite, tonite, etc. Although the last two are not necessary since "ight" is pretty consistent. Keep common clusters of letters so that it still looks like English. Do it in in stages over a 100 years , making changes every 15 years or so. I'm mostly aiming at ease of reading vs ease of writing.