Congrats for thinking laterally.
As others advised previously - pax appeal for a turboprop is not as great as a jet. But the economics......
By the way the unducted fan (UDF) did actually work and worked quite well. Refer
http://www.flightglobal.com/articles...-propfans.html and maybe another that might lead you to more details
http://pdf.aiaa.org/preview/1987/PV1987_1733.pdf
Perhaps a rear mounted UDF similar to the MD80 test might have a greater appeal.