If Voyager had a transwarp coil...

[Jaespol]

...they got one in Dark Frontier, I don't see why they couldn't remake one or replicate it.

And what about that mobile emitter? They managed to figure out how that works pretty well why didn't they replicate one of them? They could have had lots of holograms running around the ship to help them!

Gah! So many inconsistencies, its hard to bear!

 

[Tachyon]

Because there was assimilated alien technology and materials involved, unknown to Federation.

There.