I don't know whether it's possible or not. Introduce collaboration of sheets between two or more systems with different users through which they can view and edit the same sheet simultaneously just like one does in "Pages" and "Numbers".

Justification:

This type of collaboration will eliminate a need to share sheet each time it gets modified by either party involved in the discussion or calculation. This will also promote Soulver as others will have to install the app if one needs to collaborate over a particular sheet.

Example: If you are calculating budget or expenses of a vacation for a group of friends, everyone in the group can simultaneously gets involved with that sheet through this feature helping them view and edit(if the owner of the sheet provides permission to edit) at the same time.