The bridge is part of a system that includes the saddle(s), pins and if we are speaking of the mass on the sweet spot of the top this also includes the bridge patch top thickness and the bridge plate. My view is that all of these things work in concert... or not.... to efficiently transmit vibration to the box to move air. With this said you could weigh each element and determine a percentage for each component that each specific component comprises in the "stack."
Or, in other words I don't think that any one thing in the stack such as just the bridge is as consequential as some may think.
In the repair business we replace bridges all of the time. This means making a new bridge from scratch. For vintage stuff we carefully select a nice piece of maybe BRW if that is what we are replacing and make a nice, new bridge. No one is weighing the old bridge and making any effort to match the mass of the original material in the new bridge beyond using the same material/species.
In nearly 20 years of replacing bridges including on some pretty valuable stuff such as pre-war Martins and vintage Gibsons and for some very discriminating owners never once has anyone ever suggested that a change in the bridge including it's mass resulted in a change in the tone of the instrument. Some anecdotal information for you.
Or, in other words I don't think that bridge mass is as important as I once thought it must be. It's important, it all is but my view is shifting over time to much more consideration for the instrument as a whole and as a system and how it performs.
There is also the issue of the individual box and what it takes to drive it at an optimum level. Pins are always a good example of what I am getting at here people ask about tonal differences in changing pin materials such as bone, brass, ebony, etc. We are pretty sure it's not the material that makes any discernible difference (if there is one...) but we are pretty sure it's the change in mass over the sweet spot of the top that may... may make any resulting difference. Along with this is the fact that some guitars perform better driven harder and vice versa..... Lots of variables.
And lastly tradition such as the Martin style of building a guitar has resulted in some pretty good instruments and no one ever weighed anything for most of them.
Luck is in play too, always.
So not a good answer from me, nothing definitive and that is my point the amount of mass that may be optimal for the components that make up the bridge stack on the sweet spot of the instrument is going to be as individual as how that box is built, out of what, volume of air that can be moved and even the human hitting the thing.
We all have something, some number that we think may work for us and I do and did too but I question this number when I consider the ultimate function of the bridge in a "system" approach to the instrument. My number is also all I know and I certainly don't know the half of it if that and another number may be better for another situation/instrument.
What a number is good for is as a control for the bridge viewed as a variable when analyzing what one has in comparison to another example/instrument.
With this said I think a range.... of numbers for bridge weight is much more acceptable than I once would have thought. You can compensate for the overall amount of mass on the sweet spot of the top with plate thickness, saddle thickness and height (slot depth, etc.) pin material and bridge material and even top thickness in that area for those interested in fine tuning.
Complicated I know or just make a Martin belly bridge or pyramid bridge and slap that puppy on there and call it good.
