I think making the mousebite tab a component is the best you can do. You can then include that in the PCB file, which has the benefit of making it an explicit part of the PCB design (ie, making sure the tab or the breakout process doesn't cause problems), and then replicating it across all instances in a board array. Depending on how you want to panelize, you can include half of the tab on the board and then draw the other half as part of the panel (works best if you're tabbing from instance-to-instance), or draw the complete tab and the full outline of the routed areas as part of the board (works if you're only tabbing instance-to-panel). The latter may require a fair bit of copy-paste, but if you're careful with grid and snap settings it's not a big deal. I have a separate set of layers for board outline/routing vs panel outline/routing, so it's fairly easy to create fabrication outputs for a single board for prototypes and then for the panel via outjobs.