If you do bring VUs back do Twitch/Karthus way at least. New animations, modells, voice over, basically new everything.
good enough candidates for that category. Full VGU threatment but less focus on GU.
While I agree with your sentiments completely, I do believe that 
need to have the half-ass work done on them completed. They've all by and far had kit updates in some form or fashion (some, like Alistar, Fiora, and Shen, more than others), and Maokai has had voice work done, but the rest of them need new voice overs and ALL of them need new rigging and animations to be fully realized VGUs.
As for your list, I think and are the only ones who are good candidates for a VGU with little emphasis on the GU. and have been critically flawed for quite some time now, and they need a lot more work in order to be up to speed. Ezreal especially seems to break the game every time something new is released, and Blitzcrank is so dependent on his Q to do anything, it leaves the rest of his kit as nothing more than addendums to his Q hits. Blitz needs his kit revitalized and reinvented to give him more functionality outside of landing Qs.
Some champions have aged worse than others. If the base concept on a champion is good, making a more polished version of the model should be enough. If a champion is lacking charisma, Riot will overhaul them.
I don't see what the problem is with Shen and Fiora... other than the old VO.
All future Champion Visual Updates will be Full Relaunch levels of quality.
What's wrong with Shen?
Some Champions don't need everything updated to count as visual update, just like 
who needed just new textured models. It depends on the champion but not all of them can have equal visual updates.
