VectorWorks and SketchUp both work that way. You just press a key to select a tool, and any clicks after that are used by that tool, to draw lines, or offset them, or whatever, until you pick a new tool by pressing another key. It's great once you get used to it (for the first couple of weeks you keep hitting the space bar anyway). I don't know if it saves time, but it's a more relaxed feel, kind of a luxury feel. But you're limited to the number of keys you have. You can't use two-letter aliases.
It could be done in AutoCad by using a macro utility like Keyboard Express. You would tell KE that you want the L key to mean LINE<enter> in AutoCad. But then whatever keys you assigned that way would always send those characters to AutoCad, so you wouldn't be able to use them to type text. You'd have to do something strange like type text in Notepad and paste it in. Or you could buy an add-on keypad with a whole bunch of function keys and have each one send a command and an Enter code. But then you have excess baggage.
There's another feature of SketchUp and VectorWorks that also contributes to that un-frantic feel, and which is easy to implement with Lisp: they don't de-select after a command, so you avoid all those P's and L's. Any command that creates a new entity leaves it selected, and any command that edits entities leaves whatever was selected still selected. And in combination with that, they're set up to normally de-select all when you select something new, unless you hold down the shift key to add to the selection set. But those programs work on surfaces and groups and other containers, so it's easy to select whatever you want with a single window or crossing.
