I see so many people buying Kobos expecting a near-tablet experience and coming away disappointed. Not that the OP is one of those people, his concerns are far more reasonable in my opinion. Image zooming and much, much, much better highlighting/annotating is certainly possible for ereaders and have been implemented by others. Copy and paste (I don't know if any ereader has this function, at least the major ones, kobo, kindle, nook) also doesn't seem to be an unreasonable request, although I personally have no need for it. The PDF is very sloppy, but I don't know how much better it can be given the technology (I've tried most functions on kobos, kindles, and nooks but have only used PDFs on Kobo)
Highlighting/annotating is certainly a feature I would love to see improved. I do not use my Kobo to read any professional publications or technical documents, but I do read a lot of non-fiction where I like to highlight certain ideas/arguments that I feel is particularly good (annotating not so much). The start and end markers are extremely jumpy. There is no way to highlight across multiple pages, you'd have to make a different highlight on each page. The workaround I used with the KT was to make the fonts smaller/bigger so the entirety of the passage is on the same page. But on the KG (and possibly the latest firmware of KT, haven't tried) once I reduce the fonts, get the passage on one page, highlight, increase the font again, the highlight disappears. For anyone interested, what does seem to work every time is, reduce (increase) font, highlight, exit the book, open the book again, change the font back. A real pain in the ass. Unless I'm missing something here, in which case I'd love to know what I'm doing wrong/if there is a simpler workaround.