If you have 25 APs in a single open building, you probably already have frequency conflicts - adding more APs (logically separate or not) may make that worse. If your existing APs are all on the same channel you have a worst-case scenario to begin with.
You may be better off doing the following:
- Review the Channelization and Coverage Plan
- Re-allocate some of the existing APs to a new subnet
- Adjust coverage areas according to user count and channel
Matthew Wheeler
Chief Wireless Architect
www.BlueModal.com