Thank you for your replies.
@Allesandro
Now, I just managed to add 501 extension fields of the type "Indicator" to the BO "OutboundDelivery". As the activation takes some time and I cannot activate more than about 25 elements at once without running into an error 500, I will not go on pioneering to reach that mystic maximum. 500 should be enough for me though.
Would still be interesting to hear something about how this could affect transaction performance.
@Srivatsava
The screen "create/edit outbound delivery" (outbounddeliverycreateeco.QA) doesn't have an achor for an embedded component. If there was, would the data from the EC be included into the XML-output which provides the data source for form template editing with Adobe LifeCycle Designer?
Same question regarding your first proposal: How do I get 1:n references into that XML? Is there a way to influence which data is included into the XML?
Kind Regards
Pablo