All EU member states will have a representative on the European Commission if the recommendations of the praesidium of the Convention on the Future of Europe are adopted.
The deal also proposes a long-term president of the European Council, which could prove the most controversial aspect of the proposals.
The proposals will be a major breakthrough in the search for new procedures for democratically administrating the EU if the European Commission accepts them.
An agreement to allow each member state a representative on the Commission is problematic, however, because the EU is due to expand to at least 25 countries.
However, the proposals try to overcome the problem by establishing a core of 15 commissioners with voting rights on all matters of Commission policy. The agreement also proposes that representatives on the core group be rotated to allow each state equal powers.
Ireland's representative on the praesidium, Mr John Bruton, hailed the agreement as a "major achievement". He said: "From 1973 up to the present time, bigger states have had more representation in the Commission than smaller ones . . . now there will be firm and detailed arrangements to guarantee absolute equality".
Working into the early hours of the morning, the praesidium - whose job is to manage the drafting an EU constitution - made the breakthrough just two weeks before the EU leaders summit in Greece.
Mr Valery Giscard d'Estaing, who heads the Convention, hopes to present the draft constitution to EU leaders at the summit on June 21st and 22nd.
He first must lobby the full membership of the Convention - 105 representatives form the current 15 member states - before he can bring the draft to the heads of government.
Divisions over the text - particularly in relation to the council president - could yet scupper the former French president's plan. Large countries have pushed for the post, but smaller states are concerned it could undermine democratic accountability and create sovereignty issues.