Honestly, your approach of creating a dedicated SMBv1 share and mounting the Samba configuration into the container is a good way to keep the old protocol isolated. I'd also recommend restricting that share to the local network and avoiding any port exposure outside the LAN. It's not necessarily the prettiest solution, but sometimes supporting old equipment means building a small compatibility bridge like this rather than trying to force the modern SMB stack to do something it wasn't designed for.
snake game I’ve experimented with Samba auditing in production-like environments, and the usual problem is not the CPU load—it’s the amount of noise generated when auditing too many operations. If you changed full_audit:success to include things like open, write, rename, and unlink, then yes, a busy SMB share could generate a ridiculous amount of logs.