I think the battery life issue is becoming moot as time goes on, especially with the newer units being able to use commercially procurable batteries.
Liquid from the mouth piece could probably be an easy fix. something like the filter analogues have could be an option, although it would have to be replaced so there's one more consumable pain in the *** item to worry about.
On the atty front I'd like to see something with a predictable life expectancy, something you KNOW is going to last AT LEAST a month or something along those lines. Basically, I want to see something that won't require a bunch of maintenance.
Of course all this leads to fewer profit for manufacturers from sales of pieces and parts which in turn would lead to a higher buy-in price, but ti should all balance out in the end.
And a washable, re-usable cartridge filler that works and is not a hassle. I love dripping, but when I'm out and about it's much easier to use a cart I already filled and not have to worry about dripping every so often.
And frickin' laser beams.