Commercial office basement use??

[Cor Bay]

Have a contract on a 10,000 sq ft commercial office building which the main floor is almost completely occupied. 

Currently, the basement is only about 10% occupied by main floor tenant storage.

The rest of the basement is almost gutted and wide open (except load-bearing walls). Many years ago it was small office-type space but there is no outside light at all.

As I already will own the building and this space is wasted what could I put down there? Is there a market for lower-priced rent in basement units or not? Thought of document storage space but imagine most companies have digitized most of that by now. 

Any ideas especially those that currently lease out similar type of spaces. 

Thank you