Apart from having one fewer line for spells, the quick-mark menu is just more functional than the normal spell menu. Merging the two would make the quick-marking functionality easier to discover, and allow getting rid of the awful :Z binding. Same could be done for the skills menus.

After playing Cataclysm DDA for a while I got a simple (at least to me) idea. Why wouldn't you allow to swap action keys (letters)? That what you can do there with inventory and bionics for sure. If changes were preserved not only per save but were loaded for new characters from the last character played one shouldn't even had to set letters again ever.
It's very different from the current setup but it's nearly ultimate level of costumizeability and convenience (at least to me).

Instead of quick-marking, I've been longing for an option to have the spells appear in the order they are learned. It's annoying to play e.g. an elementalist and cast Frost bolt from letter B and then when you level up it's all of a sudden D instead.

Can you please submit a separate issue here for this? It's a very interesting idea but too big to do right now.

Quick-marking spells can now be done directly from the casting menu. Consequently the key binding to quick-mark spells has been removed. Additionally the dialog for casting a spell (when some have been quick-marked) has been completely revised to be a lot more useful.

Will definitely do, just give me a several days. Will properly document and share screenshots from Cataclysm DDA as well.