I love the idea of being able to lock them out of those things, even if it is purely to avoid selling/breeding/releasing them accidentally. To improve the navigatability (if that is even a word...) further, I would highly suggest the following:
a. consistent order throughout the menus - It is highly confusing that one menu (hunting for example) lists wolves based on den order, while other menus (for example breeding) list them alphabetically and yet others based on age/ID. I haven't even been able to figure out what the order is supposed to be in selling. But having them consistent would be nice. An even bigger plus would be if you could pick the order, and have all 3 available to choose from (den order, ID and name, both ascending and descending)
b. adding search and filter options. Depending on what is needed for a specific menu, I can imagine search options based on name, breed, level, cooldown status, breeding compatibility, synergies and attached companions (or even ideally searching for specific companions in hunting) could be veru useful.
c. Bigger menu options. Especially for the selling on the flea market, I feel your pain having to scroll through them 6 at a time, without even the ability to jump to a specific page number. I think I've mentioned it elsewhere already, but I really think the Flea Market specifically needs a seperate page for selling, rather than a very small window in an already overfull page.