i would like a shit-ton of loot, hahaha!
i'd love a hacking system, as i believe within a decade even cash will become intangible, we'll have PIN numbers and captcha codes to access/trade online, even in-store when purchasing goods, so pickpocketing will be relegated to stealing non-cash items like food, jewelery, cloting, weapons, augmentations, vehicles, etc.
i'd like loot to be relevant to the person or location it was found, rather than just a random collection of generated loot-style offerings irrrelevant the environment like many RPG's do. As for items, i'd like to loot all the items listed in my previous paragraph, but also possibly hacking secret files, and maybe even drugs from crime lords to sell on the black market or to key players in the political or criminal scenes, either expanding your standing for better or worse in the city, or primarily for financial or strategic gain.
in short, i'd like the loot to be more useful than just to make extra cash, i'd like it to have a real impact on the way i play the game, enhancing certain choesn paths and play-styles.
as for inventory sizes, i think it should be size and weight based, relevant to the type of person you are in terms of size, strength, augmentations, and also whether you are traveling on-foot or by vehicle (whereby a vehicle will have extra storage space), but when jumping off/out of the vehicle you must choose which loot/items to take with you on your body, and which to leave behind until you return.
i'd also like the option of lockers, drop-boxes, safehouses etc. where you can stash loot and items you don't currently need, but are holding on to for future use or sale later down the line.