this is either a question or an idea...

[thereverend]

is there any sort of switching circuit for a pedal where instead of stomping on the switch and having the pedal instantly switch to the effect you could have the effect slowly (or rapidly if there is some sort of rate knob) turn on? kinda like a "trails" mode but in reverse? i have no doubt that digitally its probably possible but i'm nowhere near that knowledge level.

is this sort of thing even possible?

[earthtonesaudio]

All that you ask, and more: http://www.geofex.com/Article_Folders/VCA%20Applications.pdf

...Application 4B. 

[R.G.]

The Mighty Morpher.

How about a four- or six-stage "ring" of effects where each pedal depression fades into the next loop? 

[Vitrolin]

maybe some sort of a blend pot on an expression pedal.