You can do it yourself - either put the blend in yourself (not hard at all) or make a new box that acts like an FX loop before the amp (buffer the signal and pass to a blend knob) for more versatility.
Compression can be brought to low levels by cutting the drive knob, and if the amount of compression you have at that point is still troubling you then it's time to stop worrying about amp distortion - and, while you're at it, playing any tube amp at any reasonable volume (if you still thought that your 'tube fatness' was anything but careful compression and clipping). For the bass bit... there's a little sort-of-secret-thing that hasn't been put out much: you can cut a hell of a lot of bass before a high-gain amplifier trainwreck and still not feel like you're getting a thinner sound. For boosting a high-gain amplifier, the blend knob is going to give you the worst of both worlds, as far as I'm concerned - you'll get the floppy attack with too much bass, thanks to the clean part (unless you have it too low to matter), and the squished tail from the compressed part until the TS is too bored with your low-input rubbish to do anything significant to it.
Curiosity really is great, but there's a FAQ dedicated solely to TS-like things and I'd love to get it closer to completion - I'm trying to make all of these questions into one massive bastard explanation and I'd really appreciate a move over to the stickied TS FAQ in the Production Tips subforum.
Jeff