Implementation of db would require 1 year if cz do it alone(the code must be rewritten from scratch), 9k usd x 12 month is big money to personal but not to company or btc whale.
Sorry but you are very far from the truth. There are at least 5 people who can give you BBR running on the latest Bytecoin or Monero code for no more than 5k-10k usd.
You are right, probably the best option is not to reinvent the wheel, but I don't think cz would do the copy paste his work is always original. In LD project cz made db implementation not rocksdb, lmdb, cocoa nor mocca but different thing.