There seems to be quite a bit of variability in terms of how cash flow reporting is done, this makes it difficult to come up with a "one size fits all" solution here. I noticed many accounting software applications leave this to other 3rd party apps like floatapp.com.
We're not averse to developing a native solution for cash flow forecasting, but it would be good first to have a dialogue about how exactly QF users would expect the business logic to work.