Currently if you increase the rent on a property it changes the calculations forward and backward in time. It would be nice if you could track increases in rent through time instead of only as a single snapshot.
big +1 on this one. it would be great if leases were a historical record, not just a snapshot of the current state. As OP mentioned, when one lease expires and the information for the new lease is update, all historical financials go wonky because the pro-forma now reflects the latest lease information. Being able to keep documents and records associated with a particular lease would be a huge benefit.