Dock feature - short click launch, long click sub dock

[irw]

I am currently using awn, but have fiddled with cairo.
One feature I like in Cairo is the sub-dock, but I have a question:

Is it possible to have an icon on a dock (cairo or others) which when clicked once will launch an application, but with a long click or double click, will open a sub menu?

For example: I have an icon for thunderbird which will open my email profile. Sometimes I want to open an alternative profle, or open an alternative email app, and if I could do a long click and have the alternatives available, that would reduce the number of icons on my dock.

I know I could have an email sub dock, but that would mean clicking twice to open my email program -- and I am lazy!