It seems its mosty the distance for your stands is the problem.
Assign vehicles to stands for pickup of baggage.
I also removed a bottleneck here.
And assigned these to stands.
And I removed 2 bottlenecks here. (since they had to go all around your wing.)
For someone who never builds with open ended funds, its very hard not to optimize stuff, haha, I sold loads of vehicles and now are like; all the non used assets cost money, whats up with that 
And whatsup with all the AVGAS trucks? you have no GA.
Just small things;
- minimize traffic (assign stuff to stands)
- build your baggage pickup/dropoff closer to stands.