It is not yet time for Mbappe to move to the Arab league, he is still quite young and must continue to set records in Europe so he can become a legend. In the end Mbappe will make his way to the Arab league for an incredible fee, following in the footsteps of other current legends. Saying this just because of money, of course and that can not be denied. Who appreciates them and gives more then they will move. If Arab League clubs can participate in the Champions League it will be an extraordinary combination, the euphoria of the stars will appear in full, attracting the interest of many people and their fanatical fans.
Mbappe is still having a long term jorney to play in the top league. He never touched la liga or EPL leagues which means if mbappe is career is still continuing but that's his choice if he was willing to leave from PSG to join in saudi club. The PSG already putted incredible fees for european player to get him.
Arab will never ever able participated in UCL caused by it was on the different continent. Approving arab to play in EPL has the same meant if the UEFA was violating its own rules. Mbappe is still having a long time to go to be one of legend int he club like real madrid or something else.
He shall go to the premier league or la liga to face strong competition with a different atmosphere. Mbappe will not go anywhere other than la liga or premier league.
At his young age, Mbappe can certainly make a lot of history in his future career, whether it's becoming a big legend or breaking many records in the coming seasons. So for now, Mbappe focus is only on PSG and hopes he can bring PSG to the UCL trophy this season.
He should leave PSG for the big league, La Liga, or the Premier League. PSG club and Mbappé cannot get the UCL trophy with the current team situation, and he will be wrong if he continues to extend his contract with PSG. If he wants to become a legend, join Real Madrid, where there is enough quality to help him.
Regarding whether the Arab League can participate in the Champions League or not, they must first comply with financial fair play laws. Arab League won't be able to compete with European leagues. I take the example of Chinese football, with a professional tournament called the Chinese Super League (CSL). It caused a similar fever when it brought in many big names with attractive salaries. And Chinese football did not develop or participate in the World Cup after that.