Hi Martin,
To my knowledge there are only 3.x Export DataSources possible right now. In your case this is not an issue since you generate such an Export DataSource in BW system A and replicate it in BW system B.
Re. the error you are facing during activation of the replicated 7.0 DataSource, I found SAP Note 2113639 - Activation of Hierarchy DataSource - GP_ERR_RSAPTH3. Please review the SAP Note, implement the referenced SAP Notes and run the correction programs if applicable.
Best regards,
Sander