I've attended close to 100 Arena/indoor football games in the past 22 years or so. Once had season tickets for the NJ Reddogs/Gladiators and later the NY Dragons who often drew larger crowds than the Islanders. Ironically enough, I think Vince should have went the indoor route the first time in 01. That was when the AFL was gaining interest nationally after Kurt Warner's SuperBowl win. The original XFL "Wrasslin" gimmick would have connected with the arena fans better than traditional football fans. The AFL crowds in the early 2000's were large, rowdy, and had a carnival like atmosphere. The Florida teams were always the best attended, Tampa in its hey day drew 18k+ and had a few games around 30k at the old ThunderDome. Orlando always drew close to sellout crowds pre 2008 shutdown and Jacksonville still draws 8k or so in whatever Mickey Mouse league they're currently playing in.
As for the rules I'd like to see if a merger comes to fruition. Elimination of the fair catch is near the top, although I would like to see the kicking team be able to down the ball as well. I'm in favor of CFL sized fields and 12 on 12, however I feel a compromise to 4 down football may be needed. Keep the XFL kicking rules, the CFL overtime and clock, and keep 1 man in motion like the original XFL and AFL.