What upgrades could I add to an Artillery Genius 3D printer to make it even better?
The best upgrade you can carry on with is an alluminum bed with a made-on-purpose silicone heater that you can order from Keenovo in China. Then, insulate with 3mm cork and stick it with 3M high temperature adhesive sheet.
Apart from that, I would recommend changing to a BONDTECH extruder and an all-metal custom E3D V6-style hotend. Bi-metal heatbreak. 5015 radial fans for both, the extruder/hotend heatsink and as layer fan. Direct mobo wiring and Klipper firmware.
There are other upgrades such as improved flexible couplers, belt tensioners, anti-vibration feet, anti-wobble, stepper motor driver cooling…