I'll address some more aspects of the OP.
I own the footswitch that came with the M9, but probably would not use it for gigging. If I did, the most likely feature I would use is the mute. The pull mute on the Master was a poor choice if you ask me. It's pretty much impossible to use the mute function without accidently changing the level. Keep in mind, a slight bump on the Master results in a very noticeable change in level

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My philosophy on using an amp factors into why I don't see the footswitch and voicing filters as an attractive option. While I can certainly appreciate the idea of using a variety of different sounds live, I view it as unrealistic. In fact, I typically find it ranges from difficult to impossible to even get one sound that I am really happy with. Perhaps I am just too darn picky. Regardless, there is no way I would be happy switching between the various presets without having the time and ability to nominalize levels and tweak the tone across all presets.
The primary role of my stage amp is to serve as my personal monitor. The intent is to hear as clearly as possible without blowing out the room.
I generally use the amps controls to dial in what I need to hear to play well. Before dialing in the amp I set the controls on my bass as follows:
Volume: Wide open
Bass and Treble: At the center detente
Blend: On my #1 I fade slightly to the neck. On most other basses I fade slightly to the bridge.
Piezo: Polarity set for clarity and focus rather than big loose lows. Piezo volume slightly above mid-way. This adds a bit of air and smooths out the attack a bit.
I usually run a DI between my bass and amp, so the amp has no bearing on the signal the audio tech is using to deliver bass to the house.
During the show, I use the bass's controls to tailor my sound for some songs. For example, I might fade a bit to the bridge pickup and bump the Bass control to compensate for the thinner sound. Or I may dial back the piezo and Treble if I play with a pick.
If I need an overall change, I reach for the amp.
Also my sound is generally clean and free of effects. This isn't really a factor with the Carbines because they are clean machines. Even if it's possible to gain up to preamp to get some grind, the taper of the Master would make it impossible to use the extra gain. As a result I run the gain lower than I want, so the Master is easier to adjust.
I would be more inclined to use the footswitch with the Titan. I have Channel 1 set up to bypass the OD circuit. This results in a cleaner, more solid state sound. Channel 2 has the OD circuit engaged and dialed in just below break up. IMHO this gives Channel 2 a looser, bloomier tubey quality. So I could see switching between Channel 1 and Channel 2. I could also see the Solo boost function as potentially useful.
I don't really see much benefit in switching the Titan's OD in and out without changing channels. The OD circuit has a fairly noticeable baked in tone, that is darker and seems to have a bit of a mid-boost. I wind up adjusting the tone controls on Channel 2 to compensate for the OD circuit's voicing. Basically my goal with using the OD circuit is to change the feel, rather than change the tone.
Regarding the ability to use a variety of tones live. Years ago I built an IEM-based PA system. It used electronic drums and had no instrument amps on stage. I spec'ed a top of the line rack-based Digetech processor for guitar. For bass I spec'ed an ART SGX Nightbass, which was also a rack-based processor. The idea was to program and save a variety bass presets, so I could tailor my sound to better suit different styles of music. Unfortunately the Nightbass was backordered and did not come in until after I left the group; so I never got to try it out. I think the idea has potential with this sort of system, but I think it would still be challenging and labor intensive to pull it off well.