The hotkeys for speed are actually hardcoded in at the moment (keys - and =), I'm trying to figure out why the audio controls on most laptops control the speed. It'sa weird/awkward bug. I'm thinking that it has something to do with how the audio controls function. I'm hoping to find a work around for it next patch.
I agree with the premise of the game controls being mouse only (also, this helps make it touch-only someday). I have a bunch of work I'd like to do to the interface, but GUI work is the bane of an indiedev's existence during Early Access. Things change to rapidly it's a constant tug back and forth adding, removing and redesigning things. The current GUI is the third complete-from-scratch rewrite, and we're inching closer to a forth one soon.
In InDev 29b (Time permitting, otherwise it may be InDev 30) I have plans to completely gut and rewrite the input code to prep for touch screen support. It'll be the first step in starting the forth version of the GUI. Although the full rewrite likely won't happen in InDev 29b or 30, but somewhere around 32-33 you may be seeing it.