First off, I completely agree with this being a terrible idea because of the logistics and it just doesn't seem like there would be any way to have a fair playing field with all the travelling involved.
The one point I tend to disagree with though is the fan support, imo a franchise in Europe would have a pretty good shot on being successful in the right area. Not sure how a franchise in London actually would do, if it wasn't successful/competitive and once the novelty wears off.
But take a look at the end of NFL Europe, a far inferior product to any NFL franchise and far worse when it comes to quality of play fwiw: Last seaosn they played, they had 5 teams located in Germany plus the team in Amsterdam. There were teams in Cologne, Dusseldorf and Frankfurt (the other two being in Hamburg & Berlin). If you look at it from a geographical standpoint, a franchise in Dusseldorf would put you into a 150mile radius to 4 of those former NFL Europe cities (Cologne, Dusseldorf are pretty much next to each other, Frankfurt & Amsterdam about a 150mile drive) plus if they played their games in the ESPRIT arena in Dusseldorf, they would also be like 20min from the international airport in Dusseldorf and the stadium is state of the art and allows somewhere around ˜55.000 in attendance.
Actually the team located in Dusseldorf, playing in the old arena that got demolished to build the current arena, had an average attendance >30.000 per year during the last couple of seasons of NFL Europe, so without the competition of nearby franchises in Cologne (and the Frankfurt Galaxy, which had a rather big following in the Frankfurt area), they might actually do really good attendance wise, even more so because Dusseldorfs soccer franchise is struggling in 2nd division play and Cologne just got promoted back to 1st division, so there is kind of a void in the sportsmarket there.