Everybody will benefits big markets means every seller have more chance to find buyers and and buyers can get better price because of the increased competition.
Free movement of people will help to increase tourism in all countries and more opportunity to find jobs for everybody.
Best education institutions will find more students and students easily find best schools / Colleges and University which offer the best education for affordable price. Therefore benefiting both students and Schools , Colleges and Universities.
Free movement of capital and good will increase efficiency, competition and reduce price for buyers everywhere.
More businesses and jobs will be created. Simply because : - more opportunities to find customers because of the size of the markets.
Stability and Peace: - If our economies depend on each other, we are less likely to fight each other. More likely we will sit on table and find solutions by solving our problems on the table.
Cultural enrichment, lower cost of travels and because we are bigger Institution we can negotiate with other powerful entities EU, China, India and USA from stronger position than if we do as individual countries.
Win win situation for everybody.