To answer your question in short, no, there is no way to modify a native task in that manner.
That said, there is a way around this, be it a little more laborous.
You're going to need to create your own camera capture page.
Here is the official MSDN Documentation and code on how to accomplish this. http://code.msdn.microsoft.com/wpapps/Basic-Camera-Sample-52dae359/sourcecode?fileId=62725&pathId=1134966225
If it were me I would make a control that pops open when you need it that does the MSDN example.
Good luck to you and welcome to Windows Phone dev. If you want faster answers hit me up on the tweeter. @Anth0nyRussell