There is one small problem which is easily fixed, that being the Y axis belt comes really close but not touching one of the cross beams, using ball chain would gradually weaken the chain over time, as well as causing some unwanted noise.
The workaround is just drill another hole, or print the part with the hole for the idler bearing shifted down a bit
Y-idler-bracket-1off
I can't see to much of a problem on the X axis, maybe just a small change in
x-carriage-belt-clamp_2off
To clamp the chain down firmly.
Just ideas from observation of Mendelssohn