This isn't a mod request or idea per se, but I've been looking for a mod like this and haven't found one, so if there is one out there already let me know.
The idea is this:
When you mine metal ores from the ground, instead of giving you a block of ore, it gives you a block of ore dust.
The ore dust must then be sifted through a sieve which leaves you with ore fragments (like the ones you get with Ex Nihilo mod)
Then you put these ore fragments into a furnace to make your ingots (or into a smeltery with Tinker's Construct).
The whole idea is to make mining and ore processing a bit more realistic as well as providing the need to have something like a sieve from ex nihilo in your non-skyblock worlds.