You're proposing military aircraft owned by an EU member state should launch from their airfields in EU, sneak over the border and land in Ukraine, refuel and (re-)arm - and perhaps get a quick paint job too and have the aviation equivalent of their serial numbers filed off - then start attacking Russian forces in Ukraine, and our plan would be basically to hope that the enemy with apparently complete air superiority plus satellite capability might not notice?

I'm firmly anti-war; that plan sounds like a great way to drag the EU and/or NATO straight into this one.