Couple of Approaches which comes to my mind are :

Approach 1 :
There should be the configurable Parameter in the org.jboss.ejb.EJBDeployer which will be used to set the default TX attribute .
The attribute should be used in the BeanMetaData to configure the TX attribute when not defined .
*********
if (result == MetaData.TX_UNKNOWN)
result = MetaData.TX_REQUIRED;
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This will get applicable to all the Containers .

Approach 2 :
Having the custom server side Interceptor which will
1) Get the BeanMetaData from the container
2) Check if the TX attribute attached to the method is Default(TX_REQUIRED) , if it default then change it to the NotSupported