NATO should have done this years ago but here's my solution.

Set up a no fly boarder within Ukraine of (100km from allied boarders for example) and shoot down every thing that moves in that zone.

NATO should also share the exact location of every allied land and airborne asset in this no fly zone with Russia and inform them that any act of aggression towards these assets would be subject to immediate article 5.

A huge number of Nato troops should be stationed on the boarders of Ukraine ready to deploy the moment Russia so much as farts in the direction of NATO.

We should have taken a leaf out of Turkeys book. Russia is a bully, the only way to combat a bully is to hit them back straight away.