I've just come across this document which does confirm this area will be accessible before the park opens.
'The proposed new seating and gathering area will provide a location for visitors to dwell when they arrive in the morning prior to the rides opening, and after they have passed through the ticket kiosks and security/bag check. This will assist in reducing queues and improve guest experience.'
It also states that the stage will host up to 18 shows/events over the season in addition to the entertainment already provided. So sounds like they're planning additional events over summer maybe? I know they used to hold some concert type events (back in 2015/16 maybe) unsure how successful they were?
'In addition, it is proposed that the stage will host up to 18 shows/events over the season for bands where the music will be louder and more like a concert format (capacity of 2,000 guests). These events will take place through the year. To protect residential amenity, noise levels will be reduced at 11pm to the pre-agreed park levels.'
'The only new activities will comprise up to a maximum of 18 days per annum where events can take place up to 95dBA within the audience area. These events will be carefully managed and will end at 11:00pm.'