Anyone knows if there's a method to change vCHA's maximum latency between nodes (like a timeout setting or something similar)?
I have a site connection that is barely hanging on the 10ms limit (average 8-9, some peaks above 10) and I'd like to know if there's a way to increase this tolerance by just a little bit (like 15/20ms).
Then you probably shouldn't be using vCHA. The latency exists as a check threshold so the solution can work. Fudging that number is going to cause you nothing but grief. It appears you just can't use it between those sites.
A maximum network latency of 10ms is a hard requirement for VCHA. See: vCenter HA Hardware and Software Requirements
If you can't meet this requirement, the use of VCHA is not recommended and it's basically an unsupported setup. Therefore, there is no officially supported method to set this threshold higher.
Basically I would consider to separate both sides anyway because of this high latency. Usually connections with this high latency are not as fail-safe or stable as you would expect for such an infrastructure (like a direct connect, dark fiber or something else on L1/L2).
Similar to what daphnissov has already said, I would suggest to think about 2 vCenters in linked mode, each managing the components of its site and using VCHA only for local high availability on each site.