On a project I'm working on, we're using exactly that approach - stainless when we know it'll be permanent, and zinced when it's temporary or exploratory. Due to the ancient qualities of the hole (from a structural and a historical perspective), we're trying to keep bolts to a minimum, and using trees where possible as additional anchors, but the expense of the stainless means some zinc ones have to be used lower down - it's all coming out of my pocket, so it has to be cost-effective! I'm using the Raumer Hang-Fix stainless with the double cones in 8mm and 10mm with Minox and Rock hangers.
For conservation reasons I don't want to have a rusty mess down below in 20 years, hence the minimal approach - and I'm using relatively posh zinced bolts too for the same reason - Fischer FAZ IIs.