> the commissioner responsible (Vestager) is somewhat likely to leave the commission after the May elections anyway, because of another pro-competition decisionNah, EU commissioners are very unlikely to stay in their post when the Commission changes anyway, regardless of performance. That's because they are an expression of national governments' priorities at the time of commission composition (every government gets 1 commissioner, and usually tries to place it in an area it is particularly interested in - which obviously changes when a government changes "colour").
This has become even more true ever since EuroParliament obtained a meaningful vote on approving or rejecting the Commission. Because the Commission President is now a political figure expressed by the party with the most votes in EuroElections, it is almost inevitably bound to change every 5 years, when Parliament changes; when the President changes, the whole Commission usually changes as well. I fully expect this to happen this year.
In the past, Commissions would change on a different schedule, without any real vote, and it was mostly seen as an administrative body anyway. This meant a President would not change until it effectively resigned or lost the trust of all national governments, which in turn allowed other commissioners to stay on if they were already working together well, with EUParliament just rubber-stamping. This changed after the corruption scandal of 1999.