I'm more likely to purchase a second unit rather than pursue the DIY path. I've had enough experience to know my limitations, especially given the propensity for damage to the required parts. Still, a DIY kit would be of great interest to many.
There are several folks in my local audio group that have put together some amazing products. One is now using an LDR based attenuator, but is frustrated at the poor channel to channel level tracking. I'm looking forward to demontrating my balanced LDRxB for him. My bet is he'd snap up a DIY kit if it were available.