The totally different piano idea is good. I don't know if the Kremseggs can be chosen as one of the initial instruments -- if so, the KS2 C.Bechstein 1899 is wonderful and would be a good smaller piano to be paired with a big grand.
Alhough if you like electronic instruments, starting with the electronic pack would give you a crazy number of instruments. After adding KiVIR + Legacy (C.Bechstein 1896 + V3) add-ons, you'd end up with:
Electronic: MK1, MK2, W1, R1, Pianet N, Pianet T, Electra-Piano, Clavinet D6
Acoustic/Pickup: CP-80
Acoustic: K1, C3, M3, Pleyel 1927, Erard 1922, C.Bechstein 1896, C.Graf 1826, D.Schoffstoss 1812, A.Walter 1790, J.E.Schmidt 1790, J.Schantz 1790
Other: Cimbalon, Grimaldi Harpsichord, Blanchet Harpsicord, Neupert Clavichord, Tubular Bells, Church Bells
Counting them up ... a whopping 26 instruments.