"Based on conversations with industry leaders, some companies may consider remote working for 30 percent to 35 percent of their workforce on a more permanent basis," the report added.

Some banks have already revealed their office return plans. Capital One, for instance, said that it will not have any broad return to work until at least September, the report notes.

Some banks with retail footprints have remained open, using drive-thru facilities to avoid contact, the report said, noting that 80% of Chase branches are open with reduced staff.

But in other parts of the industry, Deloitte said, a few companies are evaluating real estate space requirements based on the number of employees who worked at each site. One insurance company CFO said they hope to convert offices with fewer than 10 people to remote models.

Deloitte's survey responses reveal that restart plans were likely to be role-specific or geography-specific, or a combination of the two. Other factors were density reduction, sanitation, and employee support measures in their return-to-work strategies, the report said.

There are some factors that are unique to the banking industry in real estate.  For example, some banks are developing touchless interactive teller machines for drive-throughs, reducing the need to have tellers onsite. But the lack of available turrets, which are specialized phone systems for traders, along with potential compliance concerns, may require traders to return to the trading floor, Deloitte said.

"Extra planning will also be needed for office towers to ensure distancing measures are followed in elevators and lobbies so people can move throughout the building in an orderly and timely manner and avoid crowding," Deloitte said.

One firm's simulation showed it can take as much as two and a half hours to move people into and out of a fully occupied downtown office tower, revealing the need to stagger entry and exits, the report said.

"Corporate real estate leaders will have to look at contracts for leased space to determine who would be responsible to implement these changes and will need to work collaboratively with landlords during the planning and implementation phases," the report said.

Once they decide some employees will return to their office, bank management will need to review social distancing measures such as seat-sharing policies, structured shared-seating programs, staggering work hours and using large meeting rooms for smaller groups. Some firms are now deploying contact- and workspace-tracing app, Deloitte noted.

The stakes are high. One investment management leader felt that their firm's brand and reputation, in the long run, will be influenced by how it manages employee and customer experience.