New tool suggestion: Extractor Thread - Sky Alchemist

This tool would be pretty simple. You would hook it up to a vessel and to an emitter, and all it would do is extract the matter in the vessel faster than the emitter would, forcing the emitter to work faster. It would be cheap, probably pretty easy to add, and would save time.
Bonus: Capped extractors: capped extractors would matter from a vessel until there was only a specific amount left in it.

Yes, the slowness of the emitters is sometimes annoying.
It is actually partly due to the algorithms that manage how many units may sit in a given square at the same time.
I was thinking about a more expensive emitter that would be faster - but actually I think the good thing about the extractor is that you could add and remove it, depending on the actual situation, without having to add and remove the whole emitter.

The problem I would see with speeding up the emitters is how that would work when attached to anything but a vessel, since usually it is the other object that caps emission speed