I get the OP's idea and thought about posting a similar request awhile back. I know that Planet Coaster is a taxing game even for decent PCs, especially as parks become larger and more crowded, but as more themes get added (hopefully), particularly space-intensive stuff like Safari or Waterparks, some users who want to put in something of everything are indeed going to be pressed for room with the current boundaries. There are two potential solutions I can offer for how to make it work...with the caveat that they may not be feasible with Planet Coaster's current engine, but that's for the devs to tell us.
1) Free-form parks whose outer boundaries are dictated by the placement of rides/pathways/etc.; the boundaries would spread outward as you add more stuff, enabling you to build a park that isn't necessarily confined to a large rectangle.
2) You could have transit stations connecting one park or themed area to another, as is the case with Disney World. Things like hotel complexes and parking lots take up valuable real estate that could be used for the actual park in the game's current state, but by giving users the ability to connect multiple spaces of land via monorail, road, etc. those things would offer those who wish to employ them a means to do so without intruding upon the park itself. For example, one space could be "Disney World", one could be "Disney's Animal Kingdom", another "Epcot", and then you'd have a hub with hotels and such. By loading each area separately when you go between them to minimize the total number of resources/objects/Peeps/etc. at a time, it would spare people's PCs from exploding.
Anyway, those are just a couple of thoughts, though I highly doubt either is likely to happen; there are far more important and higher-priority things for Frontier to still do with Planet Coaster at the moment, and I doubt that either idea is really feasible from a technical standpoint. But it can't hurt to throw it out there, I guess.
