Thanks for the suggestion. We have added it to our user request database for consideration in future releases.
In the meantime, you can toggle between Delay A and Delay B by using an external Aux Switch. Plug an Aux Switch into the Aux Switch jack and enter System Mode (Hold down the Right Footswitch and Encoder button for a few seconds.) Scroll the encoder until you see the AUX SW menu, then press the Encoder button. On the left side of the display you can scroll to KB1 (knob 1.) On TimeFactor KB1 is the Delay Mix knob. (The knobs are numbered KB0-KB9 starting from the left.)
If you assign KB1 to your Aux Switch (you'll have to pick TIP, RING, or T+R to decide which switch you want) then you'll be able to switch between Delay A and Delay B by pressing that Aux Switch button.
As for your second suggestion about accidentally changing values, the current solution for this is to enable "Catchup." This is found in the System Menu under UTILITY.
When Catchup is ON, you have to turn each knob to its saved value before it becomes active. This is great for live performance because it prevents accidental value changes due to kicking the pedal, bumps and vibrations, etc.
