i think we all know people who would like to go everynow and then dont even bother trying for tickets knowing how scarse they are.
On the rare occassion that anfield isnt a sell out(early rounds of cup comp) you'll find more parents take their kids to the game because for once they can. You'll find all those who normally cant go try and make the most of the opportunity. i imagine that will be duplicated in greater quantity in a larger stadium.
Another alternative would be to sell more tickets to the away fans. Unpopular but nodoubt most teams would bring more than the 3000 currently on offer. Who knows more away fans might have a positive effect on our own atmosphere.