While there is a fairly good selection of possible Roxies, the number of available and experienced Velmas is not large. If the producers wanted to go really radical in a Velma choice, then maybe J Harrison McGee might be a possibility. McG played Velma at the MUNY at one point.
"Noel [Coward] and I were in Paris once. Adjoining rooms, of course. One night, I felt mischievous, so I knocked on Noel's door, and he asked, 'Who is it?' I lowered my voice and said 'Hotel detective. Have you got a gentleman in your room?' He answered, 'Just a minute, I'll ask him.'" (Beatrice Lillie)