I asked the same question on reddit ethereum sub, I got this.
In your scenario they (ethereum team) would then have both BTC and 50% of ether...
but, they can donate BTC now or few months later..
They can't. Here is why: (taken from
https://www.ethereum.org/pdfs/TermsAndConditionsOfTheEthereumGenesisSale-preview.pdf[1] )
18) EthSuisse Will Not Purchase ETH During Genesis Sale and Until the Creation of the Genesis Block.
EthSuisse warrants that it will not purchase ETH in its own sale. Furthermore EthSuisse warrants that it will
not purchase ETH from any third party, or acquire ETH in any manner, or acquire future control of ETH, during
the period of the Genesis Sale and until the creation of the Genesis Block.
they can buy at the end of genesis sale (over a year of time, or so) with all the BTC they raised.