Be careful what you wish for when advocating putting employment centers outside downtown. Atlanta is like that, and it's a nightmare: instead of merely commuting from the suburbs to downtown, most people now commute through downtown and out the other side! Or they commute from one quadrant of suburbs to another (and vice-versa), or from downtown to the suburbs (which is what I'm forced to do until I find a better job), etc.
Also, from a planning or engineering point of view, it's disastrous: hub-and-spoke transportation networks are cheap and efficient compared to the endless circular bypasses necessary for suburb-to-suburb commuting. And the issue is compounded when you're talking about rail transit: with roads, at least there's (theoretically) a trade-off where even though you're building segments, each segment can have fewer lanes. But when you're trying to build commuter rail you'd only have one set of tracks in each direction anyway, so building suburb-to-suburb lines in addition to suburb-to-downtown lines is completely infeasible. Oh yeah, and you've killed the ridership numbers on the suburb-to-downtown line while you're at it, so it can't get feasibly built either!