Then member states would not be contributing to the EU federal budget, but the taxes paid by the high income earning - high wealth persons/households around the Eurozone/Europlus/EU as well as the high profit making companies around the Eurozone/Europlus/EU. Collected by an IRS-type federal tax authority.
Will come back to this issue in more detail in future post(s).
(*) The same applies to other "aid" tired members of the EU "North", see the interview of the European Economic & Monetary Affairs Commissioner Olli Rehn 'There Is a Certain Aid Fatigue in Northern Europe' in Spiegel Online International, today (05/30/2011).
(What about a certain exhaustion of the firms, especially exporters and tourism, of the PIIGS and other Eurozone members, due to the long periods of uber hard Euro (vis-a-vis the USD as well as the currencies of Denmark, Sweden and all other non-Eurozone EU members as well of course China et al) since 2002?)