This is definitely a consideration for any park entry changes and something highlighted by the 1997 Pleasure Beach documentary.
I think in terms of rowdy teenagers, times have changed, and drinking culture seems to have changed somewhat too. I don't think rowdy behaviour would be so prevalent as long as there is a non-rider walk-around wristband fee and a full-day / half-day rider ticketing system - potentially paired with a tiered ride access system such as; Kids Rides, Family Rides, and Thrill Seekers. This is inclusive for the whole family then, non-riders for grandparents, kids rides for the kids, family rides for mum and thrill seeker dad to generalize.
Just to conclude the security risk element, you don't want non-paying customers in the park, and anyone with ill intent will pay to enter to cause harm regardless if it is predatory or worse behaviour. A paid entry system should also help to keep out any rowdy Hen or Stag parties, stopping them from just wandering on the park as was the issue previously during PPR. People are less likely to cause trouble if they have paid to be there and know they will be thrown out.
It is the best happy medium to enable flexibility of entry time and ridership level to the GP without the need for PPR. I think PPR has had it's day, and there is better value gained from flexible fixed pricing where you gain your profits on purchase regardless of what the customer does within the park after that point.
It would also be much easier to calculate ROI from marketing efforts too by calculating ticket purchases by ride access tiers and by full-day / half-day duration correlated to promotions, and to better identify ridership levels i.e Kids Rides, Family Rides, Thrill Seekers and appetite for duration on park as well as attendance levels throughout the day.
There's also a marketing point around the wristbands being accessible for all age ranges, where older or less economically adapt customers may not have access or the understanding of smartphones and app installs for ride access. There's certainly a positive spin, and the wristband is always something you can retain after a visit for a memory box or scrapbook. I know I have old football ticket stubs, festival wristbands and so forth stored in a box. Anything to put the phones away for a few hours is a win for families too.
...That sounds like going back to the old books of tickets...
Differentation for varying groups...family books of tickets, general books, white knuckle books, and a nice souvenir ticket on the end of the book, and flexible prices on the day for books of tickets...just like it used to be!
Older or less economically adept riders are catered for, and the park takes its profit in advance...the tickets are sold however many are actually used.
And the park has clear information on its return on investment, and a clear record of the most popular rides.
So, paid entry and tickets...looks like back to the future, but it works really well...and no more massive queues, back to a maximum ten minute wait for most rides.
POP is crap, and is killing the park.