The software does permit the bank. Doing side-slips at 39k is foolish.
Not an answer either, but you need to speak to them directly anyway. For the PIC to help you, there would need to be a process within the company. Otherwise, he's actually paid to reject such suggestions.
The airline does have the means to ask Airbus directly, who are in general very helpful in assisting the customers. For your query though, the most likely answer is:
We'd never tested anything like that and namely airflow stability at engine inlet is not researched for excessive angles of incidence (at Mach 0.79)
As you understand the impossibility to test that with other passengers beforehand, surely you do not want to be there either when the first attempt takes place.
On the practical side, 1-2° does not sound like something outside the normal wobbliness. Is that enough?
N.b. for photo taking, the smoothness autopilot delivers might be preferable but that yields no sideslip. Over longer periods (3+ mins?) it's impossible to beat in manual flight.
Appears as if 10° is critical for your case on a sharklet-equipped one.