Yes, the holes in the scales would be a bit big for rivets. On large scales they're roughly 5/16" and on small scales 3/16". Something like shield scales could work, if you also bought a punch to create your own holes. I haven't done rivets with leather before but you can get both 1/8" and 1/16" punches in the "Other Tools" section of The Ring Lord's site, with which you could add holes to shield scales.
I am considering a variety of things, tooling may be involved, yes. I'm using latigo as an example because I am thinking of incorporating the scales into collars, belts, waist-cinchers, other things where that type of leather is a good base. I was wondering if securing the scales with rivets might work (though it looks like the holes in some of these scales are pretty big for rivet heads,) or if there were other methods that might work as well. I would prefer not to sew, as sewing through leather is difficult at best and very time consuming.
Scales fasten on one end, unless modified with more little holes. Flexible fastening there at one end (nylon sewing awl cord or art-sinew) wouldn't suit, say, design of belts, such as latigo is so often used for. Are you considering chrometanned as your tough sturdy leather also? If you're bringing up latigo it doesn't sound like tooling the leather is under consideration.