I'm sure somebody's asked in the past about secondary modes for the weapons. Personally, I'm not convinced that this is necessary since a secondary, even if it's not necessarily eye-catching, needs to add some kind of useful gameplay mechanic, and the otherwise vanilla Doom experience doesn't really benefit from those (WADs outside of that are a different story).
I guess what I'm getting at is don't feel like you have to add secondaries just because some of us are asking for them, but if you have a neat idea, then by all means program it.