I just saw this UAG Case for Surface 3. OMG I want it. It has all the things you would want for the S3 and SP3. Unfortunatly, it obviously will not fit the SP3. Wonder if they will make a case like it for the SP3. Note the pen holder, that is not on the current UAG SP3 case.
http://www.urbanarmorgear.com/products/surface-3-case-red
http://www.urbanarmorgear.com/products/surface-3-case-red