I believe there are many folks paying fees to get access to grib files, I paid for an app and subscription last year myself. The issue is, these apps are only good if you have access to the internet or if you're in cell range. Some sailors I know pay for satellite phone service to get weather files and obviously emergency communication. I personally would pay for better access to get up to date weather files, I know for me it could be a life saver. So, yes I think there is a market out there for this. There is the option for amateur radio operators to get grib files via the winlink system, but you have to be in range with a decent radio. I know the Outernet antenna has to be stable and pointed in the right direction to get the best signel to download the files. Based on my knowledge so far I know this will be a challenge for a boat on the move, but many sailors find anchorage which is out of cell range but could easily setup the Outernet system and get new weather updates. I would subscribe to the Outernet system as a paid member just to help you guys give people that can't afford it better access to information. The service you provide now for free is awesome and the Outernet has been the topic of a few dinner conversations for me and my friends.
I can post a few messages on some of the sailing forms online, see what kind of response I get and report back to you. Think about the amount of the fee and how that would work. Do you have a way to transmit files based on a priority? I would consider weather files important, right up there with emergency news. Is there away to understand when certain files will be transmitted? Is there a timeframe or window to get weather files for current day and forecast? What would be the max forecast time range? If I had a description of what a paid subscription would look like that would be helpful information to post on a site. If you had a way for a member to subscribe for weather files for a certain area that may help reduce the file size.
Also, I would not want to see anything change for users that could not afford a subscription which I know is not your intention, if anything a few extra bucks could only help make the system better.
Thanks again for a great service.