I imagine that XE style case would be easiest and least expensive to manufacture, but on the other hand, the XE cases seems to be quite durable (except of some yellowing).
What I would like to see is a new XE style case that still has SIO, Cart+ECI and joystick ports but replaces old connectors for power, TV and video output with USB-C and HDMI. Maybe add second Cart port on top like in XEGS and slot for SD card. This new care could be used for modern replicas and 576NUC+ style systems, EclairXL or other future FPGA Ataris.