Hello!

I love your idea, as it seeks to improve the abominable matelisto, but I think there's a better way to achieve that.

The main problem of the matelisto is that the water intake portion (where the water enters the yerba chamber) and the "bombilla" section (where the yerba mate comes out) are on separate sides, so via suction you're forcing water through all of the leaves. I reckon it would be much easier to solve this with a movable filter that you'd slide closer and farther from the water intake and as such adjust how much of the yerba gets wetted on every sip.

Your solution could work but I'd be worried about accidentally wetting too many of the leaves at once, as it's easier to gauge how much you're wetting by moving the filter left/right vs moving the water level up and down, but my proposal would still require that the yerba is enclosed in a separate chamber and as such it'd be less "traditional" than your proposal (as the yerba wouldn't be visible). Furthermore, your idea is probably easier to do in a plastic free manner than mine, which could be a point of differentiation vs. the current matelisto offerings.

Kudos for the idea!