I agree with you that Voltz is incomplete, as it is still in very early development stages. Now that it has been released to the public I expect development will speed up considerably in terms of user friendliness (including all the things you miss). And from their ambitious goals, it is possible it will be better than the mods that you miss.
My simple answer to your question is definitely, no. Rather than add more mods, simply finish the ones that are there first, and I expect Tekkit will be a thing of the past (kind of like MC 1.2.5).
Throwing a bunch of barely compatible mods together is exactly the mess that Tekkit is stuck with now, and just one of the many reasons it is still stuck with MC 1.2.5. Starting over is a much wiser approach and thus we have Voltz.
A bit of patience is in order Scottish1900, but for now I would take ProfessorFalken's advice if you feel you absolutly cannot live without BC or IC2.
Just fyi, it is not a matter of just adding BC or IC2 to the mod package Voltz (this would be no simple matter). BC and IC2 would both have to reprogram their mods to work with the UE api in order to be added to the Voltz package (Among many, many other things) - it is a requirement as stated by the developers. Since BC and IC2 still aren't even fully compatible with each other I expect this will never happen. Starting from scratch or waiting for similar methods to be implemented into the Voltz mods is a more likely outcome.