I think what Iberia Cabin Crew make is pretty irrelevant to the argument. The fact is that there will always be individuals making more than others. It does not mean either are undercompensated or that the higher level should be the appropriate benchmark with regards to the success of a business.
As for the Mixed Fleet crews performance, they will have an opportunity to prove themselves. None of us, including legacy Crew, know definitively what their compensation will be because of that elephant in the room issue referred to by another forum member...performance pay.
The repeated tone of many present Cabin Crew which seems to belittle them before they have been given a chance to prove exactly what is going to make them "special" gives proof to the wise decision of BA to insulate them from the attitude of Legacy Crew. The vast majority of BA patrons I speak to are enthused and will judge them only on their service level.
Of course BASSA members that went on strike are going to be feeling "let down". They lost. I truly do believe that BASSA did not prepare its members properly regarding the realities and risks involved in IA. It was a treated as more of a "We'll show them..let's party" event rather than the serious and dangerous process it can be. That being said, we are speaking of adults here, they had the ability to explore the situation fully, and made their decision. To demand that there be no consequences for their actions is a continuation of their rather immature attitude.
You may be worried about your future terms and conditions but I would state that there is hardly an individual in the U.K. right now that isn't in the same position. BA has gone out of its way to try to preserve those..but the fact of the matter is that the majority of Cabin Crew members choose to be represented by BASSA and BA must deal with BASSA. BA, in my opinion, has gone out of their way to save Legacy Crew in spite of themselves, BASSA simply makes that a very difficult task.