I was in this same situation about 5 months ago. My 1/3 inch CCD cameras were great for the regional programing that I produce, but when one of my shows got picked up by a major sports network, I was concerned. Their specs required 2/3 inch CCD in 720p HD…not HDV. Since my budget did not allow for additional camera purchases or rentals, I “rolled the dice” and shot with what I had. I met the final delivery requirements and delivered on D5 to the network. Long story short, it looked great and no one ever questioned my acquisition format. I lost a lot of sleep over this issue and have gotten a few more grey hairs. For me, I made the decision that I needed to and was prepared to pay the consequences if it was rejected.
Good luck.
-Ray