Multi stock locaton data storage
I am dealing with the same question here for a 2 location store, one in the US and the other in EU.
Because i also don't want to interfere with functionalities and UX of present stock validation and control modules, my thought went also to manage inventory levels in separate entities.
I have this workflow/checkout in mind : 
- product nodes show the availibity of a product(variation) based on total stock of all inventories
- after entering delivery address in checkout, shipping rates will be calculated from both inventory locations
- customer will be presented a default inventory based on rate, estimated delivery time and last but not least stock level for the chosen products in that inventory.

The matter of splitting up the order comes in mind with this solution if product a is only available in EU inventory and product b only in US inventory, or when ordered quantity of product c needs to be shipped from 2 inventories.

So before thinking about setting up a multiple stock location solution, you should think about it's consequences to the workflow, especially in checkout and feasible splitting of shipping arrangements and related dues.

If you came up with something already, let me know.
Hope my feedback helped you making the right choices.