Post note: If you don't want the stats, I've summed the main points below.

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Using OPD (Offense + Defense) calculations (which uses extrapolated runs for offense, and defensive runs prevented), this is a simple reference to see what Escobar would have to produce at SS and Hardy would need to do at 3B...

J.J. Hardy (SS): +4.6 OPD

Offense:  +13.3 runs (i.e., 13.3 runs above average SS production)

Defense: -8.7 runs (i.e., 8.7 runs below average SS defense)

Bill Hall (3B): -6.6 OPD

Offense: -13.8 runs (i.e., 13.8 runs below average 3B production)

Defense: +7.3 runs (i.e., 7.3 runs above average 3B defense)

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If Hardy switches to 3B, his bat will be less valuable (NL 2008 splits):

Hardy (2008): .283/.343/.478

NL SS (2008): .276/.334/.404

NL 3B (2008): .265/.335/.441

(If we use BP Marginal Line Up Value (MLV) and Positional MLV (PMLV), we could estimate that the regression in moving Hardy to 3B would be anywhere between 4 and 10 runs. This is a difficult projection to make without doing the hard math, so I will probably try that later, but as an eyeballing-projection, the closest PA, OPS, and MLV/PMLV comparisons at 3B are Troy Glaus and Jorge Cantu).

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The wager with Escobar's defense is the following:

(1) He will be at least an average defender. If (1) is true, add at least 9 runs in Escobar's favor.

(2) He will be at least an average bat. If (2) is true, subtract no more than 13.3 runs from Escobar. 

What we have to bank on is that Escobar's defensive gains are larger than his offensive losses. 

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The wager with Hardy moving to third is the following:

(1) He will be at least an average defender. If (1) is true, push on Hall's +7.3 runs, which would be a +16 run swing for Hardy (from -8.7 as a SS to +7.3 as a 3B, which is Hall's 2008 level.

(2) He will be at least an average bat. If (1) is true, subtract no more than 10 runs from Hardy's offensive total, which would mean at least a +3.3 ranking at 3B (which is a +17 run swing from Hall's 2008 offense).

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Very, very basic projections, so far without the hard math (these are merely logical or conceptual projections, not mathematical. That will come later):

Escobar (SS): +0.0 OPD

Offense: +0 runs

Defense: +0 runs

Hardy (3B): +10.6 OPD

Offense: +3,3 runs

Defense: +7.3 runs

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With these projections, Hardy + Escobar would be worth almost +13 runs

(1) But Hardy must match Hall's level of 3B defense

(2) Escobar must be an average SS bat (.276/.334/.404)

(3) Hardy must maintain his 2008 level of production (.283/.343/.478)

(4) Escobar must be at least an average SS defender

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So that's the wager that needs to be made when considering Hardy and Escobar on the left side of the infield, and the possible return on all bets paying off is approximately one win (13 runs)...

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What cannot occur:

(1) Hardy is not as good a defensive 3B as Hall (-7.3 runs)

(2) Escobar is not an average SS bat (- ??? runs)

(3) Hardy does not maintain his 2008 production level (still +??? runs above Hall's 2008 bat)

(4) Escobar is not an average defensive SS (but is he still better than Hardy?)