Issues of RSPT and MRRT again

Comments on Christopher Findlay “Australia’s new taxes on minerals”, 7/07/2010, http://www.eastasiaforum.org/2010/07/07/australias-new-taxes-on-minerals/
It appears to me that both the original but failed RSPT and the new and largely agreed MRRT would have some bad legacy.

The original RSPT in the form as it was had a number of design flaws, such as the retrospectivity, the relationship between the uplifting rate and tax rates.

Of course, it also was unclear why the tax rate should be at 40%, that is, why it should not be higher or lower, even though some economists would say it was an elegant tax.

The efficiency of that tax would have been offset by the existence of two taxes (the RSPT and state royalties though the latter would be credited to offset the RSPT) in addition to the company tax.

The MRRT, softened some of the issues in the original RSPT, but as Findlay said it was agreed in a negotiation and a very short negotiation indeed due to the particular political environment.

Of course, the MRRT has a much narrower scope that is another serious shortcoming to start with that tax.

On a different note, if the purpose is to replace the royalty with a profit tax, then why would or could it not be done by just adding an appropriate percentage point to the company tax rate for mining companies?

The company tax is a profit tax and the new tax is another profit tax and why to have all the fuss to have two profit taxes on the same mining companies but using different accounting? Wouldn't one profit tax be more elegant in terms of simplicity and efficiency to both the government and mining companies in terms of accounting and bookkeeping?

Some may say that companies may have different content of mining. But that could be accounted for at least as easily as the two different company profit taxes applied to those mining companies.