An Item Lock would be nice, and it should be easy enough to implement; wouldn’t it just be a toggle that’s an extension of things like Staff of Herding, or the “Lost” Pages, which already can’t be vendored?
Although, in my opinion, a better option would be something that lets you mark or label items. For example, something that lets you change the color of the item’s outline in your inventory/stash, or maybe adds a colored dot, star, or triangle in the corner of its icon. For example, I would personally want at least 8-10 color choices, because then I could mark stuff to keep for the AH, and stuff for different characters / classes I have, so when it all gets thrown together in my stash, I don’t have to stop and figure out what goes where.
Instead of having to check every item, find out why you're keeping it (if you're keeping it,) go to the spot in your stash where you want that item to sit so that it is with others from the same "group," drag and drop, then repeat for each item... Instead of having to do all of that mess, you could simply go to your stash, right click everything into it, and get back into the game, all the while knowing you won't need to spend 30+ minutes reorganizing when you get back- everything is labeled. Sure, you might have to reevaluate what you're keeping because of the lack of room for all of your items, but that's a whole other issue...
Anywho, I believe this would be a better solution, because it would solve multiple issues at once, rather than having to create a fix for each issue individually.
Edited by ShadowHado#1348 on 11/2/2012 8:40 PM PDT