Couple suggestions regarding the design.

Does the battery block need all the rounded corners, and does the chamfer have to be flat?
The reason being the number of tools/positioning that would be needed.
The vertical rounded corners can be done easily with an endmill, at the same time as the holes are drilled for the threads.
However the rounded corners on the top, will either need a rounded edge cutter (probably not the proper name, but not a common cutter regardless).
The chamfer will either need a chamfer cutter (more common than the above cutter, but still not common placE), or for the part to be repositioned at an angle.
For the chamfer and top rounded corners, if you don't require them smooth, then they could be profile cut with a ball nose cutter which would result in a stepped finish. If needed the steps could be sanded/polished out after, but doing it that way would loose some accuracy.

The chassis insert looks easy enough, other than would need flipped to get both sides machined.