Well, there's a few things: I'm not sure why the housing can't be relatively proximate to the jobs, since most of these suburbs aren't actually that physically large. And while some transit is obviously still going to be necessary, figuring out ways to move people around a smallish suburb is just a considerably less Herculean undertaking than ensuring everyone in the metro area can get to the suburban job centers in under an hour or two, at the appropriate times for blue collar shifts (i.e. first thing in the morning or late at night).
And more broadly, while neither approach is easy or effortless, focusing almost exclusively on transit leads to an absurd conclusion: a region in which a handful of extremely disadvantaged neighborhoods act as warehouses for struggling blue collar workers, who are imported into the suburbs each morning and out each evening. In the meantime, they're mostly denied the benefits that generally accompany living in a prosperous area, while the two- or three- or four- hour round trip is a constant obstacle to continuing employment and eventual advancement.
It's because we haven't acted to avoid this arrangement that "transit equity" keeps coming up. Every time someone writes to the strib and complains that SWLRT isn't an "equity train," remember that this objection is in part possible because it's imperative that regional transit serve the function of exporting workers to job centers. A better housing policy would, if anything, open up broader transit possibilities.
The time frame isn't as long as you think. And it's not like transit goes up overnight, either: the light rails have taken decades to come to fruition and years to build. In the same span, we've subsidized many thousands of affordable housing units and undertaken to preserve many more. If we'd been building in the suburbs all along it would have been more than sufficient to transform the region; even starting today, a new housing policy will bring workers to the suburbs a lot sooner than the SWLRT. Houses get built a lot faster than trains.
As for simply swapping urban ghettos for suburban ghettos, well, I honestly just don't think we're at a point where that's an issue. For years, housing and transit policy has been premised on the idea that North or, say, Frogtown are somehow vulnerable to gentrification. Nothing of the sort has occurred. What you do see is growing concentrations of poverty in certain first-ring suburbs, but those also aren't the suburbs with a booming job market or affordable housing shortage.