Does Abantecart support extensions using vqmod? If not, is there a workaround?
AbanteCart does not support vqmod.
AbanteCart concept is based on 'true extension' and hooks to controllers and templates.
You can check these documents:
http://www.abantecart.com/document_wiki/index.php/AbanteCart_Extension's_Developer_Guide
http://www.abantecart.com/document_wiki/index.php/Developing_Extensions_and_Extension_API