There would be a contradicted between mbappe and messi. I know that how harsh argentina fans were mocking mbappe by losing against argentina but those people forgot that if mbappe has even won world cup title in 2018.
If both can work together and that will be so good for PSG but i think that there will be a contradiction between both. As far as i can see some season already passed by mbappe and messi in PSG without champion league trophy.
Both Mbappe and Messi were very outstanding in the World Cup, moreover, in the final, Mbappe was exactly super enough. Although his team lost to Argentina, we all know how the his performance of Mbappe, is really outstanding.
If both Messi and Mbappe are really able to unite their strength, solid, and also support each other, actually, PSG should be the strongest team right now. However, they also still have Neymar who is also very talented and his performance is also awesome enough so far. They also have a strong defense, like Hakimi that will probably become more motivated after the World Cup, and still many talented and string players there. But, we know that with this lineup, PSG was not able to rise the UCL trophy in the previous season. Are so many superstars of footballs in a club playing together at one time will not effective because of too much focus on different players? Well, the UCL will be started on Feb 15. And this will not be easy because PSG will meet Bayern. Actually, with the squad lineups, PSG should be stronger and win the match, except that Mbappe probability to transfer to another club as expected.