To a certain extent that is basically what I just proposed, the only thing kept over is the Haudenosaunee Confederation style of how a matter is decided on, arguably it actually conforms more since the second house being able to propose a matter is a significant deviation from how the Haudenosaunee do it, for them the roll of the second house is for the smaller member nations to be able to have their say after the two biggest nations have already come to agreement on the issue at hand, and to be able to send a matter back to them to reconsider so that the big guys can't just gang up on the smaller nations.

Historia Civilis did a pretty sweet write up of it all and honestly the Senate being a conditional block as opposed to a generator of legislation on its own feels more like how a "bicameral" legislative system should actually be designed to work properly.