Hi Tau,
My understanding is that there are no releases that support both Mesh and the 1250. You may be able to load a Mesh code on one of the WLC's within the WISM and a different code with 1250 support on the other WLC as long as they are not in the same Mobility Group;
Cisco WCS can simultaneously manage multiple Cisco Wireless LAN Controllers running different software versions. Cisco WCS running Software Release 5.1 can simultaneously manage Cisco Wireless LAN Controllers running Release 5.1 to support Cisco Aironet lightweight access points and Cisco Wireless LAN Controllers running Release 4.1.192.17M to support Cisco Aironet mesh access points. A single Cisco WCS can manage these wireless LAN controllers up to the maximum number of controllers and access points supported by Cisco WCS.
Note: Cisco Unified Wireless Network Software Release 4.2 for Cisco wireless LAN controllers does not support Cisco Aironet 1520, 1510, or 1505 Series outdoor mesh access points. These access points are supported by Cisco Unified Wireless Network Software Release 4.1.190.5 (or a later release that supports Cisco Aironet mesh access points). Cisco Unified Wireless Network Software Release 4.1.190.5 is part of a specialized release train that only supports mesh access points. If your network contains both Cisco Aironet mesh access points and Cisco Aironet lightweight access points (for instance, the Cisco 1240 Series operating in local access point mode), separate wireless LAN controllers must be used for the Cisco Aironet mesh access points running Release 4.1.190.5 and the Cisco Aironet lightweight access points running Release 4.2. A single Cisco wireless LAN controller cannot run two software releases simultaneously. All Cisco wireless LAN controllers that support Cisco Aironet indoor or outdoor mesh access points in the same network must be running the same software release.
http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps6521/product_bulletin_c25-471258_ps6973_Products_Bulletin.html
Hope this helps!
Rob
