At the end of the day personal experience is the only thing that will get you the right kite & size for conditions and style.
There are just too many variables, and personal taste is a big one.
For example some people like riding really powered, whereas other prefer to be lightly powered but move the kite a lot to gain power when needed.
Then there's board size, rider weight, water conditions, air temperature, etc.
It will just be a nightmare to navigate, and at the end of it all, you will just go for the kite you already have.
I don't think many riders want to go through a complicated algorithm to choose between an 8m Neo or a 9m Dice for an exact set of conditions (which will probably change).
Most people serious riders know their kites well enough to pick the right for the conditions. And the kite sizes are usually 2 or 3 apart, unless you have too much money.