Being pushed in is not going to be your problem. Since your hatch is on the bottom, any time you make a turn, or do a loop, the weight of the battery pack is going to be pushing out on the hatch. I don't see any stiffeners running lengthwise on the hatch. Also on picture 1 you have a hole for 1 hatch, but on picture 3 you have two hatches.

Instead of running the ESC in the fuselage, why not have it in the cowl with the motor? That will solve two problems at once. It will be easier to keep cool, and the weight will help balance the plane.