Some manually synced objects are more critical to sync quickly than others - you might have some that need to sync a large amount of data (which might tie up a significant portion of the transmitter's bandwidth) but can do so slowly while others you'd like to respond immediately.

Currently, the bandwidth limit for manually synced objects seems to be instancewide, so if there's a single bandwidth hog it'll penalize everything. Having a way to set a QoS or priority value on a gameobject would allow the world author to select what suffers and degrade gracefully when bandwidth limits are exceeded; it would also greatly simplify bulk transmissions.