It's definitely a possible solution for the impedance issue. The only thing left would be to make sure that the line-level device can work with the lower signal strength of the guitar signal, which is usually possible when the unit has an input level adjustment. But from what I got in previous posts, Drak is not into building electronics devices. And in his own words, "I'd much rather get the right effect off the bat and not have to buy another effect to make the first effect work correctly, if you follow. Just means more knobs, more weight, more rack space taken, and I'm trying to keep it compact and simple." But a simple solution might be to get one of these. It could be tucked away in the rack case behind the other effects.
While I was on the axess electronics website, I saw something else that might interest you, Drak. Instead of a footswitch for your Rivera amp, you could use this. It could be controlled by whatever MIDI pedalboard you use. You might find their stuff a bit pricey though.