A renal cell cyst (instead of a carcinoma) sounds like an unusual diagnosis, but I'm not a doctor. What happened with the originating renal cancer - kidney removal?

Radical resection and fibular (or other bone) flap reconstruction is major surgery, but it may be your best option. Some people here like @hrhwilliam have had a very similar surgery in the mandible rather than the maxilla.

Have you sought a second (or third) opinion from a highly rated cancer center? Is genetic testing of the tumor potentially useful?