It is possible but it requires taking the switch apart, for now at least. Some of the stick lights (3 LED, 3AAA stick anywhere) have a forward clickie and you could probably put one in a C2. Some one did it with a Fenix. I can't help with the technical details.
I have done it, it's a trivial mod, and it's transformed the light. Taking apart the switch is easy, it can be done using a small screwdriver to remove the threaded retained ring. Then, it's just a matter of putting a forward-clickie switch in that will fit the space, and completing the contact with a metal washer of some sort (and possibly adding some electrical tape to prevent contacts from shorting out to the side).
I used the McClicky switch and it works great, though I had to cut the spring and apply a bit of a solder blob to the tip to keep it from scraping the back of my batteries up.
Another advantage of using that particular switch is that it's made it possible to tailstand the light if the light is on -- doing this with the reverse clicky would cause the light to go off once the switch is partially depressed.