Aruba 2540 doesn't support virtual stacking, does it?
So the question is really about a no-go scenario.
OTOH if you have two (or more) stacked switches (two with VSF or more with backplane stacking) this means that the stack fabric forms a virtual switch, in that case no issue are there about implementing a LACP Port Trunking from a thrid device (Core in your diagram) which terminates into various members of the stack (let's say LACP link 1 to Member 1 and LACP link 2 to member 2, just to be clear).