I do these variations with my midi controller. I can attach a modifier, and then vary the value I'm sending to achieve the desired results.
Respectfully, I don't think you're correctly understanding the issue. (Or at least, you seem to be solving a totally different problem.)
I can't think of any MIDI Controller (including LF and RJM) capable of addressing the
particular issue that this WISH addresses.
Here's an example:
Your Preset has 4 Scenes, each set to use a different Channel on Amp Block 1:
Channel A: Clean (Fender Vibroverb),
Channel B: Grit (Fender Tweed),
Channel C: Crunch (Marshall Silver Jubilee), and,
Channel D: Metal Distortion (a Soldano, perhaps).
It also has an Expression Pedal which you want to roll back (heel-down) for Rhythm, and forward (toe-down) for Lead.
On your Clean sound, the difference between Rhythm and Lead involves changing the Gain from about 4 to about 7.
On your Grit sound, the difference between Rhythm and Lead involves changing the Gain from 5 to 8.
On your Crunch, it needs to go from a Min of 6 to a Min of 9.
On your Metal Distortion, Gain needs to go from 4 to 6, and the Mid control needs to go from 0 to 5.
Now, your footcontroller is going to be sending the same values regardless, from 0 to 127. The 0 is heel-down; the 127 is toe-down. And they'll always be on the same CC#, as well.
Inside the Axe FX III (or II) an Expression Link is established with Min and Max values, plus other things (damping, curve, etc.).
The WISH is to have these links have separate Min and Max values for different Channels. We want Channel A to go from 4 to 7; but Channel C shouldn't have the same Min and Max values.
And, we don't want to hear the Mids changing for all 4 channels; just for Channel D.
I can't imagine
how you'd accomplish this, unless Fractal implements this WISH.
I think the point of channels is to circumvent the limitation to which you refer. For instance, rather than attaching a modifier to gain, you duplicate the same amp on all 4 channels, and you set the drive to whatever you want it to go from clean to mean, etc.
That's a very different use-case, and I don't think it's what most people want to use Channels for.
Channels aren't so much for different Gains on the same Amp; that's been do-able with an expression pedal on all Fractal products for years. And, if you use Channels for that purpose it isn't a smooth change. That would be a step backwards.
No, I think Channels are Fractal's answer to the age-old Mr. Potato-Head dream: "I want an Amp with the clean channel of a Fender Blackface Deluxe, the dirty channel of a Marshall, and the lead channel of a Legacy!"
But that's precisely why we want different Expression Control settings on a per-channel basis.
(Nobody thinks that the "sweet range" of a Fender Blackface Deluxe -- for any of its controls! -- will be the same as the range for a Carvin Legacy, for the same control.)