Alright, I have added B.A.S.E into my modpack and it looks like the dusts dont melt in the Tinkers Construct Smeltery? I could very well be missing something, but in the B.A.S.E configs i enabled most of the metals (you know, trying to use the mod for its intended purpose lol) and didnt see anything in the Tinkers configs.

Are there molten versions of the metal already? BASE currently doesn't add liquids, its next on the priority list.

Yeah, getting the thermal expansion versions of the ore, dust or ingot produces the liquid metal in the smeltery just fine. Actually now that i think about it, the BASE version of the ingot may actually smelt. But I'll have to wait until i get home to test.
Also, since im here, is there plans to make it a config option to drop the BASE version of an ore regardless of the ore mined? Useful for people that want all the ore to be from a single mod, and/or when a lot of mods add the same type of ore. (There was a mod that did this in 1.7.10 and i couldn't find one, seems like it would be a good fit here)

I'd be willing to consider it as an opt in solution

well, im not quite sure what happened but everything from BASE works just fine.
And im sorry, but what do you mean with "an opt in solution"?

Basically a config that defaults to false, but that one could turn on to force other ores to drop base versions

that would be really cool, just as an option for people who want to clean up their ores a bit without having to reset their world. Going to close the issue though, since it isn't happening.