If I read it correctly, you want to either have straight from comp to amp, or bring in the others at once with a single stomp?
Do you also want to mix the 'dry' and wet signals? Ie "A+B" on the second ABY?
If you simply want "wet or dry" then a single bypass looper will do it for you for around £25 ("off" is straight from input to output, and "on" engages whatever loop you have connected to it)
If you want to mix the signals with control over volumes, the SFX Loop Logic will do that, although it's more wonga.