One thing you could try as a sort of middle ground between your design and having a parallel taxiway is to make a sort of traffic circle so that planes enter a one-way loop for all of your A/B11-18 stands. As it stands now, a plane going to A13 has to wait for A15 to leave. That is very slow since the entering plane has to wait out by the remote stands to enter the stand-access taxiway. By making it a loop, sure, all planes have to go through the hole space, but since they are going in the same direction, they are only delayed momentarily as another plane turns in or backs out.
To do this, I’d add a connection between A12-B12 (or further out depending on your actual baggage handling facility size) and A18-B18 and set up the proper one-way points. A11 and B11 would be on their own little stubs off the main loop.
Another thing I might consider is moving the baggage handling facility to mid-field, between A14 and A15. That would cut your longest baggage truck trip in half. I think that would pay off compared to the additional conveyor belt distance. The only possible problem there is getting your workers to the middle of the taxiway island if you were to do the loop plan I suggested; I’m not certain if there is a way to get a crosswalk or service car stop to service that.
Finally, less of an idea, but more of a question is why have separate A & B secure areas? By doing this, does this prevent the problem of a passenger going to a restaurant somewhere in A when their flight is in B? If so, I’m going to stop making giant single secure area airports.