How? There isn't much trade between Africa/Arabia and Europe other than oil, some agricultural products and used cars/outright waste.
> The natural beauty that attracts tourism can help repatriate the talented diasporas.
That's already the case in Croatia, many pensioners who worked in richer European countries retire back in Croatia because they can "live like kings" from pensions that would barely fetch a 1br micro apartment otherwise. For 500€ you can get a 75 m² flat in the center of Rijeka - in Munich that would be around 1500-2000€.
And those in working age... it's rare for them to return to their homelands for that reason.
> The question is whether brain drain, crime, and corruption are due to incurable pathologies or symptoms of transient disadvantages.
Neither, in my opinion. "Incurable pathologies" is bordering on racism, but it aren't "transient" issues on the other side. What's needed is massive amounts of wealth redistribution across Europe, combined with throwing the whole lot of political elites into jail (and that's also sadly valid for Germany, just look at Andreas Scheuer or the MPs who allegedly got huge kickbacks for anti-corona masks).
Basically Europe would need something like what the US did post-1945: a complete clean-up. Absent that, I'd also accept a revolution of the masses, but that isn't on the pipelines anywhere except in France...