In my data base I have Walt Disney as one of my Alternate Great People, the idea being that he can appear as either a Great Artist (Movies) or Great Merchant. Here's my write-up:
Modern Era:
Great Merchant Walt Disney (Walter Elias Disney)
American entrepreneur in entertainment. Created a huge film and animated cartoon production entertainment business from 1928 to 1964 CE, and in 1955 CE opened Disneyland, the world’s first Theme Park entertainment center.
OR
Great Artist Walt Disney (Walter Elias Disney)
American animator and film producer. A pioneer in film animation, also produced both animated and live films, holds the record for greatest number of Academy Awards won for film production (22).
Great Works: (1928 - 1964 CE) all films
Snow White and the Seven Dwarfs
Fantasia
Mary Poppins
(And, obviously, 19 others!)
Since Disneyland, and later Disneyworld, were both built 'from the ground up' from bare ground, I would not make the Theme Park an Upgrade from an earlier building, but a tile-filling Improvement built by 'expending' Disney, creating a tile that provides Tourism, Happiness (X Amenities) and Gold - and the amount of all of them produced goes up with the number of Aerodromes with Airports within X tiles (OR the Amenities are applied to Every city in your Empire with an Aerodrome/Airport, but that has the potential to be very OP)
Alternate Great People can appear in either of the two lines: Great Merchant or Great Artist, but whichever is grabbed first by a Civ eliminates the other from the game - can't have a cloned Doppelganger Disney wandering the map!
On your other two:
Kurosawa only died in 1998, or just over 25 years ago. That means any game company may have to deal with copyright issues depending on who holds the rights to his works now.
Likewise, Agatha Christie (or Lady Mallowan) died in 1976, or 48 years ago, so her works are probably also still under copyright restrictions. The laws on copyright protection make any modern artists in almost any medium hard to use in a game - or anywhere else. If it weren't for that I'd be arguing strenuously for the inclusion of J. R. R. Tolkien and Walt Kelly as Influential Great Writers/Artists!