I find the concept and definition of 'power' to be exceedingly complex and somewhat ambiguous.
I suppose its necessary to define what we mean by power. You can have potential power : the means to express power : this could be wealth or resources. Of course a large voodoo chest implies potential power : if used. But then we must consider practical power : a million TI's are just junk without several million turns to actually implement them. Thus voodoo power will always be constrained by turn possession and acquisition. If turn limitations mean one can only ever use say.. 1000 of a card then the player with 10000 is not actually more powerful than one with 1001 cards. There is potentially more power but practically.. there is not.
I suppose one must also consider the application of power : which is more powerful : 10 levis that sink a 60att SotL or 10 levis cast on a nuisance pirates 40att frigate? Context can matter as well as ability and skill in applying power : 50 TIs cast on a 50mil population do not carry the same weight as 50 cast on a 1.5bil population : that also applies to BD's.
Is 5billion sitting in a bank untouched for months as 'powerful' as 5million worked hard to generate an income far above that figure?
Influence is power : it provides control and can provide vast income : but it's transient power and its also deceptive : context matters again. 50million in one port is control : 50 mil spread across 20 ports is just a large bill daily to stop it bleeding away. Meanwhile it matters nowt if your nation is weak. 20 million in the right nation and right port can be the path to wealth and resources.
So...how we weight each aspect of potential power matters. But should we also weight application of power? A skilled pirate may have few ships and few voodoo along with limited infrastructure yet apply that power exponentially and punch far above their notional weight. A wealthy merchant with vast fleets, wealth and infrastructure can be a hopeless fool when applying that potential power to practical means.
It's a complex business and immensely difficult to measure accurately nevermind rank
That said I would welcome such a metric but not invest too much belief in its efficiency : as a fun top list it could add flavor to the stew but not a lot of sustenance.