In order to remove a dynamic property, save the "meta.DynamicProperty" object that is returned by "addprop" and then use the "delete" function of that object.
In order to save the "meta.DynamicProperty" objects, create a struct "sig_meta" that maps from the property name to the "meta.DynamicProperty" object. This was a property of the "A" class.
If you want to hide the "sig_meta" from the property list of your "A" class, use "Hidden=true". This allows you to still use the property, but it will not clutter your Command Window outputs.
Finally, in order to delete the dynamic property, use "delete" on the field of the struct "sig_meta" in your "A" class. Then, call "rmfield" to keep the struct and the "B" class properties in sync.
An example is attached.
To play with this example, execute
>> obj = A;
>> obj.Sigs
>> obj.sig_meta
>> delete(obj.sig_meta.prop10);
>> obj.Sigs
>> obj.sig_meta
>> obj.sig_meta = rmfield(obj.sig_meta,'prop10')
>> obj.sig_meta;
