The 1815 Rattrapante PC Tourbillon is an true icon but personally, I will keep the RG 1815 Rattrapante PC and acquire either a platinum Tourbograph or a 1815 PLM Tourbillon to complement your RG 1815.
In that way, you will get all the complications in the 1815 Rattrapante PC Tourbillon but in 2 different watches. Also one in platinum and one in rose (love the rose gold from Lange!). Just IMHO 😄