The theory is doable. "Signature-less" antivirus engines/programs can also be affected.
Think of a MITM attack. Similar premise -
Adding another software program (any) increases the attack surface because it adds vulnerabilities.
Maybe scanners could become significantly faster - or set to not scan upon download - but allow initiation of a manual (right-click) scan as a workaround.
Nothing is 100% secure. I realize how little I know every day - but this site and community helps add to that knowledge base.