Deeper negative interest rates, a new bond-buying programme and relief for struggling banks are all on the agenda, producing a rarely-seen level of public division on the bank's governing council.
President Mario Draghi, who will yield his seat to departing International Monetary Fund chairwoman Christine Lagarde on October 31, could yet tie her hands for months -- or years -- to come with his final moves.
Over the summer, Draghi stoked confidence in an upcoming policy package.
In July he reiterated the "possibility of actions in the future, if there is no improvement" in economic conditions.
"This might be his last stunt, but we expect Mario Draghi to conquer the barricades once again" around the council table, ING bank economist Carsten Brzeski said.
"The costs of waiting or only delivering parts of a big package and then trying to get ahead of the curve at a later stage will be higher," he added.
Central bankers have for years failed to hit their inflation target of just below 2.0 percent, despite unprecedented interventions -- peaking in a 2.6-trillion-euro ($2.9-trillion) bond-buying scheme from 2015-18 and negative rates on banks' deposits.
Now US-led trade wars, weakness in emerging markets and the risk of a no-deal Brexit are slowing growth.
In the second quarter, economic activity in the eurozone expanded by just 0.2 percent compared with January-March, while annual inflation fell to 1.0 percent in July. Its leading economy, Germany, is forecast to slide into recession in the third quarter.
Pictet Wealth Management strategist Frederik Ducrozet underscored risk of markets' expectations for future inflation becoming "de-anchored" from the central bank's aim.
The resultant bets on lower future inflation could turn into self-fulfilling prophecies.
Ducrozet suggested Draghi could announce 600 billion euros worth of new bond purchases, as well as a cut in the deposit rate banks pay to park cash with the ECB, from -0.4 to -0.5 percent.
But "dissensions within the governing council could lead to a sub-optimal decision" that leaves asset purchases for another day, he added.
Trouble could also loom from far beyond the ECB's 43-floor glass tower in Frankfurt.
"An ECB decision for further monetary stimulus could be seen by the US president as anti-competitive behaviour by the ECB," warned Nomura analyst Chiara Zangarelli.
"This could well mean a renewed focus by the Trump administration on auto tariffs."
Governors from the weightiest eurozone nations, including France, Germany and the Netherlands, are sceptical about new bond-buying.
"Is it necessary to restart purchases immediately? That's a question we'll have to discuss," Bank of France head Francois Villeroy de Galhau said last week.
Villeroy is normally seen as one of the council's "doves", more favourable to monetary easing than so-called "hawks", who mainly hail from northern and German-speaking Europe.
Even ECB vice-president Luis de Guindos insisted in late August that the institution is "data-dependent".
"Indications from market expectations cannot replace our policy judgement," de Guindos said.
New ECB staff growth and inflation forecasts, expected to be lower than in June, will provide fodder for the doves' arguments at this week's meeting.
The June outlook already trimmed predictions for both measures, with prices expected to grow just 1.6 percent in 2021 -- far short of the target.
Whatever the decision, policymakers will tweak their "forward guidance" on future policy to set markets' expectations for how long low interest rates will last.
If the ECB launches asset purchases, it will likely tie any rate hike to their coming to an end.
To quiet inevitable grumbles from banks about low rates, many analysts expect the ECB to introduce a "tiering" system exempting some deposits from the charges, which amount to more than seven billion euros per year.