Can LTM help to save on SSL certificates on different common names?

Looks to me like autodiscover.abccommodities.com could possibly be the external domain name and autodiscover.abc.com is the internal. I'd check to see what your autodiscover DNS record looks like internal - it may be going to autodiscover.abc.com and so the cert is valid for that. If you want your cert to be valid for both abc.com and abccommodities.com you have to have the autodiscover.abccommodities.com in your SAN list. TMG is a Microsoft product and likely compensated for the cert mismatch whereas F5 does not.

Looks to me like the solution is to generate a new CSR, add autodiscover.abccommodities.com to the SAN list for the cert, generate the cert, and then swap the cert out on the F5 as well as your Exchange servers.