Qantas Pilot Speaks Out, page-66

He may be overweight, and there may be a risk of stroke or heart attack, but it will be amplified by a vaccine that has a risk of blood clotting

It will NOT be amplified by any of the coronavirus vaccines. The mRNA vaccines contain no increased risk of clots and the blood clot risk with AZ comes from a condition completely different to the usual risk conditions for DVT's, clots, stroke.
If this man doesn't the employment conditions, he is free to seek employment elsewhere. I have numerous health practitioners in my close family - even before coronavirus, if you didn't show proof of vaccination for a number of preventable diseases, you simply were not employed and your registration with the national registering authorities is contingent on showing PROOF of immune status for particular diseases.