does anyone make a volume knob that would look like pickup switch, but continuous (e.g not on/off kill switch, but something that would act as a completely normal volume knob, just in the shape of a switch).

I'm really curious about how it would feel in use? If any of you ever used a guitar with something like this, feel free to share your experience.

u can make it with a 5 way slide selector switch and just add trimpots ; will work like preset volume
dont think 3 way switch woud be "economic" for it (u can basicly get 2 diferent volume levels (and something inbetween ?))
rotary switch - yeah ..but with normal potentiometer u can fine tune the volume levels, this way you are stuck on your presets.
If you're talking in terms of something like a pickup switch, the throw would be too short. That would make it way too sensitive to the smallest movement. Think about it for a moment. A standard pot has something on the order of 270 degrees of rotation, stop to stop. Something made like a pickup switch, you'r be lucky to get 90 degrees of movement. Hence, it would be about 3 times as sensitive to the smallest movement.

If you truly wanted something different, a slider pot such as they use on mixing consoles, could be installed in a similar manner to a Start 5 way switch.

Somehow though, I have the feeling that wouldn't be the look you're trying to achieve.
I'm not really trying to achieve any particular look, I just think that volume switch could be easier to use - for my typical usage (most common one are swells from 0 to 10), I feel it could be easier to control the volume while playing some note, especially if I could use a more recessed switch and position it close to the strings.

Slider pot is an interesting possibility - it's has low enough profile that I could probably have it close to strings and strum over it without problem.

Also, I just now got the idea that I could have 2 volume pots - one knob for setting volume on whole song for something like Brothers in Arms, and a fader for volume swells that could be fairly short -> sensitive.

Also, shorter movement seems like a win-win to me - I can't do a full swell from 0 to 10 in a single movement while playing a note with a pick, so I usually have to increase the gain and only swell from 0 to 4-5. Shorter path of the "switch" type volume pot would be ideal here.