Dear Andrea, and Raja
Thanks you for you reply.
I've done a double check internally. In order to deploy a SLD in 7.1, at the moment two installation type were available (NW 71 PI, or CE).
As far as I know, using the 7.1 version allow to use the FAS (Full Automatic Synchronization) - instead the automatic forwarding or export/import functionality - for the data distribution.
The NW PI 7.1 version is exactly an AAE (just the Java stack).
Maybe, the licence cost in this case could be free of charge, due the absence of any exchange of xml data, and any 3th part software incluse. Basically it's just an SLD 
But obviously, as you suggest, it would be better to ask this info directly to SAP.
Regarding the Solman 7.1 (and the relevant planning upgrade), surely it will be involved on the design topology of the SLD Landscape, due the fact that the LMDB functionality can merge with the FAS functionality of SLD 7.1
But in this case, I think that the implementation of SLD centralized directly on SM could have some impacts with our PI/PO scenario - in terms of availability during maintenance operation of SM.
Thanks.
Cristian