I'm not sure how the team would effect the NFL product, but the only things I could think of are:

 

Fans - The NFL would not move/start a team in London unless it is confident it could sell out 8 games a year. Wembley stadium holds 90,00 (86,000 for NFL) people which would make it the largest (by seating amount) stadium in the NFL. It would also be one of the most modern stadiums in the league (currently 4th, 5th once the Vikings new stadium opens). Currently the NFL have sold out 3 games this year, 2 games last year and single games in previous seasons at Wembley. The rumour going around right now is that a team will play back-to-back games in a season at Wembley. One thing I saw was the Jags hosting the Bills in London next year then the Bills sticking around for a week and playing a home game in London themselves. People who are against the idea will relate to the NFL Europe attendances however that's a terrible argument. NFL Europe was a farm for 99% arena league standard players to play, it was a "reserve" league and was never going to be a success.

 

Travel - It currently takes 5 hours 40 minutes from New York to San Fran, it takes 7 hours 15 minutes to London - just 1 1/2 hours more. This is reasonable. The biggest problem is the west coast teams heading over to the UK and I agree that could be a problem. It currently takes around 10 hours to get from San Fran to London. I'm not really clued up on aviation too much but I imagine 20/30 years ago teams would travel a lot more than 10 hours to get from one city to another. Aside from that plenty of business people travel across the Atlantic weekly and get by just fine. A 10 hour flight isn't that crazy.

 

It'll be interesting to see how it pans out. The way I see it - London is not just a singular thing, it's a gateway for the NFL into the wider world. The biggest hurdle is the first one and if they can be successful in London then it'll only open more and more windows of opportunity to expand.

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