I feel the exact opposite. I've recently been experimenting with ipv6 only via NAT64/DNS64 and run into the same problem (with steam trying to connect out to hard-coded ipv4 addresses).

I started to look into CLAT and really didn't want to have to go through the hassle of a whole new virtual interface with routes etc, when one single app can't just pass a couple different args to connect().

I actually had thought about trying to write something exactly like this myself.

I'm glad to learn it already exists.