I think it's a marvalous idea! You are right by taking the time to think it out.
If I were going to attempt this, I would build it on the site I wanted it, make the mesh form, use cement for the basin and seal it well. Yes be sure to put in a drain or two, then I would finish anything above water with hypertufa. As long as you can wrap it with some wet sheets, and cover with plastic, you can cure it well.

Just a thought...if you want it on a patio, you could build a large platform dolly, and build on it. & Make it a permanent part of the structure. Plant hostas or other plants around it, or place some 'loose hypertufa rocks' around the base. Then drain and move it in winter and spring. Would be like a huge birdbath on wheels. lol You would be able to move it wherever you want, if you change your landscaping. (even take it with you if you move) lol

How deep do you want to make this?
Are you adding a fountain feature?
Neat idea, keep us posted
Marcia

I'm hoping to make this about 2 feet deep. I don't think I'll have a fountain feature as I have a few other fountain features around the house. I was also thinking of using cinderblocks stacked in a circle, then wrapped in wire mesh. Could I then hypertufa over the outside of the cinderblocks? This would make the pond basin wide enough (and hopefully strong enough) to be a bench. Any thoughts?