Robert,
I am no expert but I am a similar situation. Your questions are difficult to answer without knowing your objectives and resources.
1) Does your film truly require a wide format? Or are you just considering the idea? Personally, I think modifying the camera is risky. It sounds as if sync sound is more important to your project than wide format so why put your 6080 at risk? If you require wide format, you can achieve this in post but then you have to be very mindful of your framing composition while shooting. I would experiment with this option before physically modifying your 6080.
2) You do not state whether you want your film to be in color or black & white. There is no best film for daylight, other than perhaps using a lower speed film rather than a higher speed one. It's all a matter of personal taste. It is also a matter of financial resources. Reversal stocks will, in most instances, cost you less than negative. All I can recommend is that you experiment with several different types of stocks and find out which ones will work the best for you and your project.
3) Same as above, but low light situations will require a higher speed film. Available negative stocks offer higher speeds and have more exposure latitude than reversals. But if your project can be Black & White, then maybe Tri-X reversal can fill the bill. Again, experiment before you start principal photography.
FYI: I have a short film I want to shoot but it's all at night time in a back yard setting. I really want to shoot this with Tri-X because I love the look of that stock (when exposed properly... that is) I do have access to film lighting equipment but because of the limited exposure latitude of Tri-X, I am not ruling out using a negative stock. I plan on shooting several rolls of Tri-X and a negative stock (either 200 or 500) and then make an informed decision prior to principal photography.
Good luck with your project and if you report more info about it, I am certain you will get excellent suggestions from others on this forum.
