https://turborenault.co.uk/threads/my-197-meglio-conversion.128866/page-8
https://clio197.net/threads/battery-light-megged-197.58700/
These threads seem to confirm what I thought. Clio alternator would definitely be worth a try.
Don't quote me but I'm pretty sure I remember my meglio used the clio alternator as I was told using the megane one threw a battery light. Might be something worth investigating, maybe a phonecall to rs tuning etc