The EU would love a highly militarized and friendly neighbor who will protect them against an aggressive other neighbor.

There is a need for both arming Ukraine AND preparing for escalation on home soil. If the initiative is pressed too hard the escalation would likely come sooner than they can prepare for.

The baggage of corruption is on hold as membership is currently in a candidate state. It's not moving until after the war, and will come with a mountain of oversight.

Fracturing the russian federation is a real possibility. But it will take time, and continued losses. If putin stops the war he avoids this but not his own downfall. He's boned either way... unfortunately he knows this.

Once putin falls Belarus is free.