Hi,
as i wrote

"Even without this limit, the total time needed for a complete refactor (read guide, write new code, test new single api, system test) it's not affordable for me at the moment."

It's not a simple address change, i need to rewrite the way CAT perform any API call.
There's a big guide about it : https://bittrex.github.io/guides/v3/upgrade
It's not a single api broken (sometimes it happens, latest was Binance and i fixed it), it's a full system to rewrite.