In classical republican theory there are three main pillars: Freedom as non-domination requires ecomomic secureness as a key prerequisite. That’s were the concept of a universal basic dividend plays a major role. Job- and housing-guarantees are necessary collateral tasks.
A mixed constitution (in the American tradition Checks and balances) requires ubiquitary balance in power. Here we can introduce the concept a new ‘fourth power’ as a consultative, the Citizens Assembly in Ireland as a role model (empowered citizenry).
As a very first step the European Parliament has to win full right to initiate legislation. Freedom-Equality-Solidarity-Common Wealth-Peace-Compliance with the ecological planetary boundaries.