While this idea of expanding the railroad to encompass the park has been talked about before, in the end, it faces a lot of hurdles.
For one, you would need tons of infill dirt to create a smooth gradient for the line spanning the perimeter of the park which has varying topography.
And before you can even consider that, there is the fact that the original manufacturer of the railroad, Crown Metal Products, went out of business in the late 1980s. The current owner of their assets, the Tweetsie Railroad in Blowing Rock NC, uses them only to maintain the currently running Crown trains. And even then, it takes a while. It took them two years to replace the boiler of the engine on the railroad at Worlds of Fun in Kansas City.
I hate to be a downer on this, but that’s just the way it is. Kings Island just wasn’t designed to have in-park transportation. The closest thing it had to such was the Skyride which spanned from Octoberfest to then the Happy Land of Hanna Barbara. And even then it didn’t even last a decade.
However, if by some miracle, a mode of in-park transportation can be built, whether it be train, chair lift, or even monorail, I would be behind it.
Also, I think that the people who think the entrance should be changed don’t fully understand the reason why it was designed the way it was.
To be a kind a of cavernous gateway between the real world and the park within. As you enter the dark and “see the light at the end of the tunnel” you are at first treated to a small glimpse of fountains and buildings which entice you to continue forward. Then, the buildings, fountains, and Tower at the far end are slowly revealed, and once you are fully in the light, the full view of the street and tower is revealed, creating a grand entrance which welcomes you to explore what is there.