Design a custom consensus protocol for a globally distributed financial ledger that prioritizes Byzantine Fault Tolerance (BFT) while minimizing latency. Your response should include a detailed explanation of the leader election process, the mechanism for handling network partitions without sacrificing safety, and a formal proof or logical argument regarding the protocol's liveness under asynchronous network conditions. Compare your approach to Practical Byzantine Fault Tolerance (PBFT) and Raft, specifically addressing the overhead of communication complexity.