A way to share items with out being in a corporation technically already exists through trade and contracts. However, what I believe most people are seeking is something similar to the diversity allowed in the real world when it comes to businesses and business structuring.
Currently as is, your corporation is setup much like partnership. where two or more people share financial and legal responsibilities, and a few are actually in charge of the corporation. IE CEO directors etc. who control the actual assets and abilities given within the corp in order to maintain a uniform front for that corporation.
A single player is basically a Sole Proprietorship.
You might want to consider adding in corporation types and maybe making some changes like for example.
Partnership Corporation - Basically what you currently have with a slight twist. Every member has basically the same abilities there really isn’t a CEO etc., First 5 members are classifed as “founding members” and all are partners. Votes are required any major dicision such as, Wars, Applications, Tax changes, friendly fire, etc. Structures can be anchored by any member with out restraint. With or with out a structure being in space this corporation due to its type would be war eligible. This would be similar to that of a real partnership.
Limited Parnership - Basically the same as above however this corp remains non-war-eligible. Can not hold sov space. They Can anchor structures provided they purchase Concord Certificates (Possible isk sink). That could cost say 100,000 isk per certificate that would be placed in fuel bay and depending on structure size consumed at 1, 2, or 4 per hour.
Full Corporation - All members that join are classified as employees, This is where CEO, COO etc. options are available for leadership positions. Also an extra option is available here where employees can receive a “salary” from the corp. Only those in high level leadership positions can anchor structures, declare war, make changes etc. You could open the stock market up for these corporations and allow the corporation to sell stock and approve dividends this would add a whole new dynamic to the game. Again this corp type would always be war eligible.
Limited Liability Corporation - Basically the same as a regular corporation but remains non-war-eligible. Can not hold sov space. They Can anchor structures provided they purchase Concord Certificates (Possible isk sink). That could cost say 100,000 isk per certificate that would be placed in fuel bay and depending on structure size consumed at 1, 2, or 4 per hour.
Non-Profit - Basically a sole proprietorship that links their wallet with the corp to allow for the purchasing of a corporate office. There would be one wallet that would be “linked” to the leaders wallet for use to rent corporate offices for asset trading etc. Non-war eligible can not anchor structures at all.
Co-Op - Basically a partnership where up to 5 can link a corporate wallet to rent an office, they don’t have access to each others wallet or linked wallet just that each can rent an office with there own wallet and still remain part of the same corporation. Again non-war eligible, and can no anchor structures.
To get more into the stock market which is sitting there at not being used. players should be able to see profit losses with corporate wallet, not so much who or what contributes to that wallet just that the business is either making money or loosing money. Just like in the real stock market they can they offer to purchase stock and those that own stock can sell it. There could be stock splits, and dividend allowences. In order to keep it simple that is, all corporations can do this and all players should be able to participate in the stock exchange. Broker fees can be associated with transactions (Another potential isk sink). Being that isk exchanged would be from player to player, and that the passive income gained through dividends would also be from player to player and not generated by the game.
Another thought would be the introduction of a corporation market system. Limited to say only the Full corporation. Sharing of internal corp merch has always been a thing with corps for a long time where they have their own stores with there own swag, or items at discounted prices etc.