When I said the economy of the greater Arab world in 1918 was essentially zero, what I mean was they had enough economy for local use, with some exports in the case of Egyptian cotton and a few other things. OTL after WWI, to the extent there was industrialization of infrastructure improvements these came from the foreign overlords - railroads, water systems, electricity etc. Yes, I know some of this had begun in Egypt before WWI but the UK had been running things there for a while. Assuming you have some large Arab entity emerging after WWI, where is the capital for these sorts of modernization going to come from? The French and the British are unlikely to loan money for this except at very high rates given the risk, OTL some of this was done for strategic rather than pure economic reasons - there are many other examples, port improvements is another. OTL some of the frankly commercial investment made by outsiders in the Arab world, such as oil exploration and development, was made when large chunks were under European control and thus these investments were seen as safer with a more stable political environment.
The above is an economic reality, that no amount of raw material export available between 1918 and WWII can overcome - cotton, wheat (for export outside the Arab world), potash, will only bring in so much hard currency. FWIW the entire Arab world OTL has, once you subtract oil and gas, a GDP equal to Finland (more or less). Sustaining some sort of pan-Arab state spanning a good chink of geography, multiple branches of Islam, multiple ethnicities, and some significant religious minorities with limited infrastructure and capital available for modernization is, IMHO, calling for Skippy & Co.
When things go wrong, who will they blame?? The Europeans, long gone, Israel (not there)? Introspection for societal difficulties is not a feature of most of the Arab world OTL.