You have several options to handle open carry. Remember that statistically people who have obtained a concealed carry license are among the safest groups in the country. In some states where they are allowed to open carry local communities have already vetted them. The problem would be those states that allow open to carry without this process.
1. Ignore the problem
2. If you have a problem in one of your offices where staff is afraid of the situation. Have someone who can approach the person individually and ask them to step into your conference room. This person cannot be judgmental meaning take either side in the gun debate. Instead approach the person stating this is a bank and wearing a gun here is causing stress with staff. They are trained for robbery situations and a gun heightens tension with the staff. Ask them when carrying openly please use your drive up window. If they become combative discuss the note passer robbery. Where law enforcement could be called by alarm and mistake them for the robber. We are worried about their safety too.
3. What procedures were established in your financial institution to handle servicing account holders during an epidemic? Can those same procedures be altered to handle open carry?