This is doable if Airwave provides a raw data session report summary which reports on every sessions summary detail as one line item with other good relevant information such as connected AP, controller, signal strength (RSSI), Signal Quality (SNR), Client username, association time, connection duration, map location, SSID & Radio Type and you can generate a report on daily basis to collect the raw data required on daily basis. With the daily raw data report, one can then use the XML query to get the data out and you can easily massage the data according to your needs.
Regarding the sessions information, it would be more useful to use a rolling past 7days data rather than a daily summary because, it will span through the two non-working days and number should be more consistent assuming there is no big change in the way the wireless is being used. With the daily raw data, one can easily do the past 7days numbers if you want. Once you have the raw data, it's all upto you how you look at the data.
Just my 2 cents.
-Tan