In my misspent youth, I worked on a 10% project that helped consolidate and free-up racks of servers so that they could be physically forklifted between space leased/owned by different subsidiaries of one of the world's 5 largest corporations (by market cap). I heard through the grapevine that the main reason for this arrangement was so that these subsidiaries qualified for small business discounts on electricity, and they wanted to keep physical separation in different parts of the datacenters to bolster the case that the various subsidiaries were in fact separate entities.
When you adjust taxes and rates based on company size (or things correlated with company size), you need to be careful about subsidiary loopholes.
What does it help Apple that they have hundreds of billions of dollars sitting somewhere in their offshore accounts if they cannot use that money?
Having these monopolies (defining loosely - whether one company or a 2 or 3 or 4) is the main deficiency of capitalism.
Unfortunately, breaking up monopolies or increases taxes is exceedingly difficult to do as large companies and their lobbying congress prevents it in most cases.
The curve used to shape the tax rate as company size grows could be tuned to mitigate many of the potential negative side effects of this.