Sounds good to me. The only issue I have thought of is that the large warm surface area would cause more evaporation than normal.

Shalom, been thinking about a similar setup with the waterwheel I'm working on installing - like the look of the water coming out from the rocks effect. I've had about an 16" water fall where I have the water from the hose going over the edge of various rock layers, most goes directly into the pond as a general stream, but with some dribbling over the rocks. I have never had a weir on the waterfall, just the hose over the rocks, sometimes I'd put a small flat stone in the water path to disperse the flow to add variety to the waterfall. I got quite a bit of moss growing on the sides of the stream (it's a northern exposure)and looks neat. Hopefully, i'll have the same concept with the water wheel, have to minimize splashing to keep evaporation under control as best as I can.

A weir is only needed when a clean wide, even, sheet of water is desired.

I think it is a great idea and one I have thought of myself as this is what is often seen in this area in the natural state. The water comes out of the rock walls in many areas and runs down.