Hi,
I’ll try to address each of your points.
- The sync feature has recently been expanded to allow syncing of directories/whole projects. If you hare having issues using sync, please submit a bug report here. We do attempt to unload assets when syncing (otherwise the files would be locked by the OS), but the feature is fairly new and not used often internally.
- We do allow diffing of ‘general’ assets via text-export. However you are correct in stating Blueprints are currently the only asset we have a custom visual diff tool for.
- As far as I know, we don’t have any plans to introduce merging of assets within the Editor (although I agree it would be a cool feature to add). We have generally found that with Blueprint usage and the multiple-package paradigm that UE4 now uses, contention for resources is fairly rare. We lock files for editing so conflicts between machines should not occur often.
The source control integration is still in active development. For instance, we will be seeing additions like Perforce SSL support coming soon. Please feel free to request any specific features that you think would be useful to your workflow.