CoreXY 3D printer designed my own required carriage, and I designed it... Due to I am using Bowden setup the carriage is without extruder. There are fixed points for belts in front and belts tensioners guides behind.
The carriage fixed on Chinese MGN12 rail guide.
There is also bed level sensor holder provided, an industrial inductive sensor.....
I used PLA for it and it works fine even when extruder 210-240 Celsius! But please use ABS or PTEG for to ensure the part will not melt in printers with covers.

My own designed CoreXY

No

Yes

0,1-0,25

60-80%

You must use supports to print the part due to it has overhangs in par of bed level sensor and fan pins\holder