I'm gonna shock everyone by agreeing.
Nerdy answer: Our SS situation is deplorable and if we look internally for a fix we're way too dependent on Jed Lowrie to hit at a level he has never sustained for a full season (not saying could or couldn't, just that he's never actually DONE it). I don't think you can count on Lowrie to the exclusion of other solutions. Especially with Lowell and Varitek already candidates for large late-season dropoffs and no production coming from the DH spot with no idea when that's likely to change. Too many things aren't falling our way offensively for us not to make some kind of move, and Hardy's a better short-term and long-term move than most.
Besides filling multiple immediate needs at once as a power hitting shortstop, Hardy is a solid long term acquisition to fill a hole we need filled over multiple seasons. And he hits well enough that if we still want to break the bank for Hanley when he starts to get too rich for Florida's blood in a year or so we can do that and let the two of them sort out who moves to third base at Lowell's expense.
Also the price tag isn't going to be low, but Milwaukee has enough needs that we should be able to tempt them with enough B-list prospects (Daeges, Bell, Wagner, Richardson) that are ready or close to ready to keep the A-list losses down. Pretty sure you could get it done with at Mike Bowden and a supporting piece (Bowden and Wagner would be a very fair price IMHO for Hardy's services and both would help fill Milwaukee's organizational needs)
Short answer: We badly need a power bat and SS is a spot we can improve by subtraction as well as by addition and a fair deal for Hardy doesn't kill us long-term. Get 'er done.