My dream ereader would be great at website viewing - I spend a lot of time looking at forums and newspaper websites and reading reviews and comments, so it would be great to do this on an e-ink screen instead of my iPad.
It would have excellent battery life, where I wouldn’t have to think about the battery for a full week of solid reading. I don’t care about spurious 'weeks', just give me an honest full week, and I’d be more than happy.
Maybe a larger screen, but without additional heaviness, I’m quite tempted by the Forma as it has the larger screen and is the same weight as the Oasis, but perhaps with the wasted space on kobo screens, there won’t be that much difference between the 7” Oasis and this.
Things on my dream ereader wish list that have already been fulfilled by my Oasis 7”:
Waterproofing, ideal for me as I like to read in the bath, pool and spa tub.
Wonderful dictionaries.
Even lighting. (Finally,

)
Larger screen.
More premium appearance/feel.
Easy book borrowing from my local library (I always have my iPad near and it’s very easy to browse and check out on that, then send to kindle from the amazon website - it all takes about ten seconds).
Great selection of newspapers and magazines from all over the world - this will always send me running back to amazon as Kobo doesn't provide subscriptions any more...
I thought I wanted the audible function, but I struggle to care about this in practice.

(Mostly because it causes the battery counter to count down in real time, horrifyingly.

)