Before you do anything you would have to read the User Agreement between your company and the companies who office you are hiring.
Then when you know what is allowed and cloud or at least public Cloud will almost certianly breach their Security Agreement with your company and result in a penelaty at the very least for your company
You will know what will be allowed but I must say that most of these places have their Agreements written to suit their needs not their customers requirments.
I would suggest you are stuck with a wired NAS or similar but this ALL DEPENDS on what the Security Restrictions you are under are. You should be on a child domain so others in the office can not read and alter your documents but if you are not then it is open slather for anyone who wants to do as they please and your Security is nonexistant.
I should also add WiFi has a range of about 550 meters and is easily crackable so just having a Secured WiFi Access Point possibly allows anyone who wants to access to your data so unless there is a overriding need I would avoid it where possible.
Of course Security may not be an issue here though I have never seen any company who is willing for everyone to have access to their data particuarly their Customer Details and transaction records.
But your alternatives here all revolve around what is allowed under the contract you are working under and the Requirments for the leasing Companies Security Rules. In most places I have done any work just altering the layout of the network will result in instant dismissal NO QUESTIONS ASKED OR ACCEPTED.
The rest all revolves around the actual layout of the Network as external access will if nothing else increase the amount of data being moved around and hence the companies costs for Internet connection.
