I'm afraid that is more complex than this and will require a lot of work in order to set the load cases.

I think that 6 sets of displacements would be more accurate, D1, D2, D3 for A platform displacements (on X only, on Y only and Z only) while B platform displacements are 0 and likewise for D4, D5, D6 B platform displacements while A platform displacements are 0. Then you can play with displacements as you wish, changing the signs and possible combinations.

Maybe also relative displacements can be used but on less complex system.

Another difficult decision will be to choose the linear, non-linear approach.

Regards,