This will be a useful reference point for you to see if any functionality desired is included in 8.5.2 and may help build a business case for upgrading.
For merging contents from a view, one method would be to build two separate NotesDocumentCollections in SSJS (Server-Side JavaScript) and join them - there should be an option for this. You won't have sorted results, but you can't currently get that in XPages anyway. The resulting single NotesDocumentCollection can then be used as the source for a repeat control.
If you're feeling brave, you could extract just the NotesItems you require and NotesIDs into an array of Javascript objects, and use that as the source. If you're very adventurous, you could use Java beans. Either way, it's worth testing with large searches to check and address performance.
For the FTSearch, are your Full-Text index options set to incude attachments? How about using a repeat / loop to get keyword documents for the databases you want to search over?