(Please note that I haven't actually got an M13 here; I bought one a few days ago and it's on the way. But I have been doing some reading about it, and since no one else has responded to your post, I will try to answer it, to the best of my ability...) (And let me first say that I play guitar, and what you are looking for is a solution that few guitarists would require. But bass players apparently have needs different from those of guitarists. Forgive me if I seem unsympathetic, I'm really not. ) ( Detailed explanations here are for possible readers not familiar with the subject under discussion. ) As you seem to know, you could run the M13 in the fx loop of a loop pedal such as a Wounded Paw Blender or One Control OCMBE Mosquite Blender Expressio (or other similar devices). This will let you blend the dry, direct output of your bass with the entire output of the M13, and will let you control the mix from either all dry, direct output bass, to all M13. This is really not a complicated solution - it's one pedal and two patchcords. Whether it's pricey or cost effective depends on one's personal situation. But it won't allow you to blend the dry signal with the distortion models and then take that combined signal and route it through the M13's other fx slots. So, although not a complicated solution, it might not be an ideal solution. (It's not nearly as bad as you make it out to be. A One Control Expressio is just an itsy-bitsy wee thing...) If, however, you want to blend the only the distortions or overdrives, inside the M13, and then have that mix go through the other fx slots, you might have a problem. I don't see how that can be done, really. ( Although I don't know if this is technically feasible, one solution that could *theoretically* work would be: split the bass output into two channels. Patch a simple two channel mixer into the M13's fx send. Send one channel of the bass output directly into the M13's inputs, and send the second channel of the bass output into the mixer that you have already patched into the M13's fx send. One potential problem here would be that the digital processors - both the main cpu and the digital to audio and audio to digital converters - will almost certainly introduce some audible latency so that your dry bass signal might be very slightly out of sync with the processed M13 sound. But as the dry and the M13 sounds will be so different, the latency might not matter at all. As for potential ground loops, or other problems, I can't even begin to guess. But because the dry and fx signals are quite dissimilar, you probably won't need to worry about the sounds being in phase. This *is* kind of a complicated solution but one can imagine that there are people for whom it will work.) As for hoping that Line 6 will implement a blend control for the distortion / overdrive models in a firmware update, my opinion is this: don't hold your breath. To begin with, Line 6 has been offering a $150 rebate on the M9 and M13; often companies do that to reduce stock of something that they intend to stop, or have already stopped. manufacturing. Additionally, the last M13 firmware update seems to have in January 2011 - the product is finished, done with, over, and it is what it is and so it shall remain, world without end, amen; I'd not expect them to devote resources to it after 7 years. ( Do the people who did the work on the M13 even work at the company now? Maybe not. Dunno. ) But also, every knob in every effects slot is already in use, so that in order to implement a blend / mix parameter, they would have to remove some other parameter. I can't imagine that Line 6 would do that. So the answer to your question "How much work can it be?" is probably "Quite a bit".