The valve "defeat" module is a crude solution that prevents the valves from operating (either permanently closed or open).
Reprogramming the computer would be a more elegant solution that would allow you to adjust the default (what the valve setting is at ignition) and which modes would automatically close the valves (if any) and if there are any other inputs that adjust the valves (such as gear position).
I would think the easiest and most sensible solution would be to zero out any signal inputs other than the console switch. That would allow the driver to turn it on or off "manually" using the switch, and not have to think through every branch and sequel of which modes and what situations they want quiet or "sport" mode to apply.
The biggest question, why would you want it in sport mode in 6th? I no longer have active exhaust, and the ONLY time I miss it is on very long trips when cruising at higher rpms for long periods.