Given that all the performance data published in the AFM/AOM is defined by configuration, thrust and speed I'm not sure, unless like JT you happen to have gathered certification data, how a pilot can account for a deviation from the prescribed configuration, thrust and speed without a great deal of guess work.
As for post v1 failures, I'm pretty sure the company will have something to say about how to handle them. e.g. appropriate SID turn backs or visual terrain clearance.
and someone mentioned earlier that TO software doesn't account for AEO SID requirements. Well it can and does in our case where we can select a specific SID with sometimes limiting gradient requirements. It will then add this limiting AEO case to the list of limiting weights. Lowest one wins as usual.