All PlanCo1 included themes should (IMHO) be default included in PlanCo2 -- I don't wanna wait (or worse, pay DLC money) for a Pirates theme in a waterpark, for example (glad to get Viking, doesn't replace having Pirates). Any DLC that doesn't use other IP (Spooky, Adventure, etc), should be included in PlanCo2 as well -- it'll take some work to move the assets over, nowhere near as much as it took to make them in the first place. I still (like, last week) look to use objects in PlanCo1 that I'm
sure are there . . . because I used them a decade ago in RCT3. There's no good reason to make us choose between the features we're finally getting (lovely as they look) in PlanCo2 and the stuff we're used to working with in PlanCo1.
Honestly, between the PlanCo1 stuff but better (flexcolor stuff that wasn't, or was poorly implemented like the Pavilions, removable bum-poles and boxes on the animatronics) and scaling (not sure I trust the -60% to 200% limits,
Lilliputian theming should be doable with tiny/huge fantasy stuff), I'm pretty happy with the existing/announced themes, just want better implementation and more in them (some gaps in building pieces filled in, more scenery that takes advantage of the new stick-to-rides features, etc).
Hmmm, Mad Scientist stuff, that'd be good. Bubbling tubes and vats, that goes with water -- jacob's ladder, bouncing power halos, electricity in general doesn't, but still.