Your challenge, should you accept it, is to have the Arabic abjad used as the main way to write the Romance languages in the Iberian peninsula (i.e. Castilian, Portuguese, Catalan, etc.), all the way to the present day, with a POD no earlier than the creation of al-Andalus. Note, however, that there need not be just solely Muslim states like al-Andalus for the usage of the Arabic abjad - it also includes the Christian kingdoms as well.
Permission is also granted to allow extra/modified letters in the Arabic alphabet (so long as the letters you are using are found in either the "Basic Arabic" and/or "Arabic Extended" Unicode blocks) - however, I'd like to see an orthography first. In fact, if you DO decide to do orthographies for at least 1-2 Romance languages using the Arabic abjad, you'll get bonus points (and a cookie if you do more than 1-2), under the condition that you post them here.