Portland Runner your idea seems very sound to me. In fact, it's one of the little tricks I employ as a competitive masters athlete. I run zero recovery miles per week. Workbouts (Coe's term), that would of necessity be recovery runs for me if all I did was run, can much more often be carried out at real training stimulus intensities if the impact trauma is removed (with a bike, elliptical trainer or a pool).
For example, when I'm in the 6-8 weeks of intense intervals and repeats leading up to a macrocycle's goal race, I can still swim very dadgum hard on a day that must be devoid of running because of muscle and connective tissue trauma. In fact, the cool water and the flutter and dolphin kicking is very therapeutic for sore legs! Alternatively, I can bike pretty solid on that swim day and be recovered soreness-wise the next day (but rather taxed systemically). So the following day might occasionally allow for a hard running workout alone or a combination of medium effort running and riding.
I find it fun and interesting to balance and tune this stuff. Perhaps more importantly, I can sustain much more quality training stimulus over time (with less "junk" miles or minutes) by cross training.
Would I become a faster runner if I ran more and cross trained less? In my mid-twenties, yes. In my mid-fifties, absolutely no. Now I can stand only so many footstrikes, hard toe push-offs and hard hamstring contractions per week, even if optimally spaced throughout the week.
But: once I've hit that weekly quality / quantity ceiling of trauma with my running, I find I still have plenty of strength and aerobic adaptation available to me with other modalities.
In sum, even if I was 20 years old, I'd have to allocate some running to recovery between hard workbouts (or take total rest) if all I did was run. The tissues gotta heal. But while they're healing I can still get real work done, if I play it smart.
Now, PR, this is just between you and me, right? I don't want this getting around to my potential competition. Perhaps we should troll out a thread about how cross training is the bane of the masters runner, and how recovery runs are junk miles; better to go hard every day, and only do it with running. You with me, buddy?