Apart from the "resort" style parks: Disney etc., I don't see why more parks can't give their guests more options when it comes to visiting. To be honest, I think the new Blackpool system sounds ok, though £5 is a little too much. If the price was around £2-3, it would be a lot fairer.
I'm basing this on the way that most Asian parks operate. A lot of them have either free entry, or a low gate price. Guests then have a variety of ride ticket options including pay-per-ride, 5-ride ticket (for example) or a wristband/all inclusive option.
It works!
Take Tokyo Dome City as just one example. In the evenings, the place has an amazing atmosphere as friends go there to hang out after school/work, get something to eat and maybe ride a coaster or two. They're having a good time and spending money in shops, bars and restaurants.
If they had to buy an all inclusive ticket (they could if they wanted to though), they wouldn't go. The park would be busy at weekends and during school holidays, when people are going for the whole day, but would lose out on money during a normal week.