Since February 2022, a new consensus has settled in Brussels: The European Union needs to grow larger. EU members once considered enlargement skeptics now agree that it's time to start thinking seriously about welcoming hopefuls like Ukraine, Moldova and Western Balkan states into the club.

The shift was prompted by Russia's full-scale invasion of Ukraine. Before then, loose plans for expanding were Brussels' favorite proverbial can to kick down the road, passed from one administration to the next while aspirant members such as North Macedonia — an EU candidate since 2005 — jumped through a series of shapeshifting political and judicial hoops to qualify for access without ever exiting the waiting room.

These days, the mindset has changed. As one EU diplomat put it: "Enlargement is a reality now, and it wasn't a year and a half ago."

But Brussels has its own homework to do if the political consensus is to become a practical path. "Before you can have a realistic conversation with the countries coming in, we have to figure out what an enlarged EU would actually look like — and that's as far as we've gotten," the diplomat, who asked not to be named, told DW. "We know the questions but we don't really know the answers to them."

Tipping the balance of power: Making decisions at 30+

The conversation has, however, begun. Earlier this month, a group of researchers commissioned by France and Germany unveiled a paper full of ideas on the workings of and pathway toward a larger union. Thu Nguyen, a senior policy fellow at the Jacques Delors Centre in Berlin, was among them. She told DW that rethinking how the EU takes decisions could prove most politically challenging.

The official list of EU candidate countries is long: Ukraine, Moldova,Albania, Montenegro, Bosnia and Herzegovina, North Macedonia, Serbia and Turkey. Georgia and Kosovo are also considered "potential candidates."

But even with 27 members, the bloc sometimes struggles to take action. Foreign policy moves like sanctioning Russia require unanimous backing, meaning negotiations can sometimes take months as member states hash out which products to ban or whose assets to freeze.

Changes to other policy areas like migration and asylum require support from a "qualified majority" of EU members — meaning at least 15 states which also represent at least 65% of the bloc's population. Last week, the limits of this political arithmatic were also on display when Germany greenlit reforms to a new rulebook for migration crises, only for fellow heavyweight Italy to swiftly walk out and leave the deal deadlocked.

Under the current system, Ukraine — with its population of more than 40 million — would become one of the most politically powerful countries in the EU. Meanwhile, each smaller Western Balkan state such as Montenegro — population circa 620,000 — or Albania with its roughly 2.7 million inhabitants — would add more voices into the mix.

"The more the member states there are, the more risk of having veto players that block decisions," Nguyen said. That could prove even tougher for politically-loaded calls like blocking EU funds to countries accused of breaching rule of law standards.

Nguyen and her co-authors therefore suggest scrapping unanimity and recalculating qualified majority voting shares to make sure a bigger EU still has the "capacity to act." Controversially, that proposal would also make it more difficult for big powers France and Germany to block agreement.

But such reforms would require a rewrite of the bloc's founding laws and need support from member states who would lose power in the reshuffle. And, as Nguyen acknowledges, "the political mood currently is not very favorable toward treaty change."

Ukraine grain dispute heralds potential budget bust-ups

Then there's the question of how to divvy up EU funds across deeper economic disparities. Most EU candidates have a lower GDP per capita than the bloc's current poorest member Bulgaria — and with around a third of Brussels' current budget assigned to agriculture subsidies, the arrival of farming powerhouse Ukraine would radically shift the current disribution sheet.

Last month, Poland, Slovakia and Hungary announced plans for unilateral embargoes on Ukrainian grain to protect their own producers from potential price drops. For the EU's former trade commissioner Phil Hogan, this shows the rocky road ahead.

"There's going to have to be huge institutional change, huge budget change and policy adaptation to the new reality," Hogan told DW. "Ukraine is a huge country with huge agricultural interests. And the notion that you would overnight be able to deal with the issues of Ukraine becoming a fully integrated member of the European Union's agricultural policy is going to be a major challenge."

"Even in my time, there were sensitivities around many trade issues with Ukraine," he added. "It's nothing new to have tensions between Ukraine and Europe in relation to agriculture — but you can imagine the challenges are going to be ahead for the European farmers in the context of the Western Balkans and Ukraine and others becoming part and parcel of the family."

Still, Hogan remains hopeful: "I am very much in favor of the expansion of the European Union and bringing into our European fold countries that otherwise could go into a different fold that we may not like," he said, making a thinly-veiled allusion to Russian influence.

"Politics is about the art of the possible and I expect that the existing member states will stretch themselves and their citizens will stretch themselves to ensure that we have our neighbourhood in a less tense place."

The end of an ever-closer union?

There are all sorts of smaller questions about the functioning of a larger EU which also need answers: How many more lawmakers would enter the European Parliament? How many more official EU languages would there be? Could each country maintain a dedicated member of the European Commission?

Given the legal and political quagmire that likely lies ahead, some think it's time to broaden the definition of the bloc. This week, as Europe's leaders head to Spain for a third meeting of the European Political Community (EPC), one vision of a wider intergovernmental set-up is on display.

The EPC is the brainchild of French President Emmanuel Macron. When he first publicly floated the idea in 2022, Macron said it could take "decades" for Ukraine to join the EU, and argued for a new grouping that "would allow democratic European nations" to "find a new space for political and security cooperation."

Today, the EPC is fomally nothing more than a talking shop, with no established structures, voting rights or treaties attached. But it is the only forum of its kind uniting its broad church of 45 invitees. It includes all EU countries and candidates, wealthy nations staying an arm's length from the bloc like Switzerland, Norway, and the United Kingdom, and even political rivals Armenia and Azerbaijan. Russia is not on the guestlist.

For Thu Nguyen and her fellow researchers, this looser structure could provide a clue about what might happen if the EU fails to agree on an expansion plan.

They suggest there could be a core "inner circle" of closely integrated EU countries, then the wider EU, then a next level of "associate members" who enjoy some benefits linked to the bloc's single market, and an "outer circle" based on the EPC, which Nguyen says would "not include any form of integration with binding EU law… but rather a cooperation based on geostrategic considerations."

EU: Ready for 2030?

But this potential multi-speed approach may prove unpopular, seen by some as creating second-class citizens in the EU's club. Ukraine's Prime Minister Dennis Shmyhal recently told news outlet Politico his country is "performing all the maximum efforts to ensure that Ukraine would become a fully-fledged member of the European Union."

The European Commission often insists accession is a merit-based process with no timeline. Still, European Council President Charles Michel recently said the bloc itself should be ready for enlargement by 2030.

Thu Nguyen also backs an end-of-decade target ​​— but, asked whether that's realistic, she says simply: "It's difficult to make a prognosis."

"This is a very long term process," Nguyen said. "We're very much at the beginning of the discussion and of the debate."

Edited by: Ben Knight