Given that manufacturers provide basic geometry data and you can provide your own basic biometrics, could the two be combined to analyse a likely best fit, based on mechanics (lengths and angles) or empirical data? Would the "sweet spot" be determinable?
A fitting session on a set up device ought to help choose but presuming someone hasn't done that and not everyone can walk into a shop and find a suitable bike in their size. In my experience even supposed experts can't always tell a good fit by looking (having experienced a contrary opinion).