Divert those military age men from Libya who are invading Italy and send them straight to the front lines. Promise them Ukrainian citizenship if they survive.
That would be an interesting discussion to have. I am not sure if it would help but the chaos would be brought to a new level.
Not to take away any satire in your post but how many refugees/illegal aliens/border crossers WOULD actually take up such and offer; perhaps if it came with their families being allowed to stay in Ukraine and receive some level of support while they fight and a benefit if they die fighting? Enough to fill the ranks and turn the demographics from losing to a more true stalemate? A better place to negotiate a settlement from?