Leaving aside other issues with your question (splitting mega-corps into "under 1M sales" units is about as feasible as disassembling a ballistic missile into pieces small enough to be OK to carry onto a passenger airliner), you did actually stumble on a correct approach to an answer of why a mega-corp would nearly ALWAYS welcome more regulations, as long as they aren't terribly crippling, in a business field with low barriers to entry and much small competition.

Compliance with regulatory regimes is a cost whose function has a floor, but grows very slowly.

I'll make up a some numbers to illustrate the idea, but it's pretty trivial - it costs at least $X dollars (say, $300k) to implement a software system to comply with regulations. It costs $Y dollars to extend that system as the company grows, but that marginal increase is significantly smaller, say $1k per $1mm in sales (that's just how those things work - it's a lot cheaper to scale up a system that already exists than to create one. I'll commit a logical fallacy and reference myself as a cite - I build such systems for a living :).

So, for a business with $300k income or less, complying with such regulations would mean they go out of business.

For a business with $600k income, complying means their income is slashed by 50%.

For a business with $3mm income, it slashes the income 10.1%. For a business with $30mm income, it slashes the income 1.1%. For a business with $300mm income, it slashes the income by 0.2%. For Amazon.com (Net Income in 2010 $1,152,000,000) it would be 0.01%.

    | Income | Compliance cost | Income drop | Comment         |
    | <$300k | $300k           | 100%.       | EPIC FAIL!      |
    | $600k  | $300k           | 50%.        | Hard to recover |
    | $3m    | $303k           | 10.1%.      | Impactful       |
    | $30m   | $330k           | 1.1%        | Survivable      |
    | $300m  | $600k           | 0.2%        | Pocket change   |
    | $1B    |                 | 0.13%       | Amazon rules!   |

So, look at it from Mega-Corp's point of view. Enacting costly regulation is a major competitive benefit for them, despite the cost - because the cost, comparatively speaking, to their smaller competitors is much much larger; and for the smallest of such competitors, creates a barrier to entry which they didn't have before.

This is why Amazon welcomes Internet tax (but not eBay whose livelihood depends on small sellers); why GE loves environmental regulation, etc...