To the first issue: Handling of big databases
I recommend to distinguish between background and foreground data sets. In a common scenario you are not interested in changing (and thus tracking of) background data sets. You could follow this approach:
Other users should also start with step 1 to 3 and then run "Repository/Fetch". This way all users have the same data sets and can continue tracking/exchanging foreground data sets.
To export your foreground data sets from an existing database. Use "Export" and select "JSON-LD" and only select the process data sets that are part of your foreground system. Linked data sets will be exported automatically. When you import it into the database already containing the background data sets, data sets should be linked correctly.