As a pretty slow writer I would love the ability to just call out info. Currently, unless it's something obvious like an sbh nuke it's easy to just spam Q a couple of times. When I need to relay more delicate (wrong choice of word I think but I'm not quite sure what to call it) information like for example gunner rush inc through x passage or something, it gets a lot trickier. To me it kind of feels like unless I'm in my base where I can run inside, I have to choose between 50% chance of dying and not typing the message.
So in essence I would love to see some way to communicate without having to throw my life away all the time. At least allow us to keep running while typing (in Killing Floor for example, you can keep W pressed after pressing T and you'll keep on running until you let go of the W key).
In the end I think that voip should be a server option.