Changed my mind mid-fermentation...can I do this?

I just brewed an American Hefe that I planned on adding raspberry concentrate to (half of the batch at bottling time). The other half would just be a regular American Hefe.

Here is the recipe:

Wheat Liquid Malt Extract 4.5 lbs
Briess Carapils Grain .61 lbs
Briess White Wheat Grain .54 lbs
Amarillo Hops 1oz
Raspberry flavoring 4oz
White Labs WLP320 - American Hefeweizen Yeast 1

However, I got to thinking...can I rack half of the batch into my secondary, and add some orange zest...and make an orange wheat out of it?

Then of course leave the rest in the primary, and add my raspberry concentrate at bottling, to the rest? Is leaving half a batch in the primary a bad thing?

Thanks,
Patrick

My take on it is that as long as there is enough fermentation still going on to flush the air out of the carboys to prevent oxidization, then why not.

No problem. In both cases, there will be enough CO2 to blanket the brew.

I tend to agree with the above posters, but they've both identified the major concern: if you rack to secondary too late in the process of fermentation, then you will have far too much headroom in your secondary, and the wort will oxygenate. (Bad for flavors.)