I never had an issue with the old lockers on Air. Place your bags in a metal cage and either have a staff member slide the door across or automate the system like on Blue Fire. Speaking of Blue Fire I’ve seen them load and send a train in 20 seconds with this baggage system so I fail to see the supposed drawback of increasing station faff.
It does depend on plenty of other factors too to be fair. Train design is one - Mack launch coasters, B&M flyers and inverts (for example) are easy to cross over the train to get to the other side to put bags in. Standard sit down coasters are more fiddly, and it takes people a lot longer to move about than you'd expect.
Culture also plays a part in this. Germans are efficient people, so they'll naturally use bag boxes on stations more effectively. British people, especially at theme parks, are a bit more self-entitled, expecting everything to either be explained step-by-step, done for them or that they can ignore the rules. This adds a lot of faff and time to the bag box procedure.
It then comes down to whether there's enough space in the station to deal with all the guests. Colossus at Thorpe is the perfect example of not enough space - you've got all the guests getting off the ride and the ones trying to put their bags in the boxes, plus staff, all in that tiny offload area. Delays are inevitable.
Bag boxes in the station can work on some rides, but it needs to be in a good scenario. Wickerman probably could have them in the station if it's explained clearly enough, but they'll probably see it as a safer option to stick with a bag room for the mid term.
