HTTP HTTPS Proxy redirect question

Yes you can do this you create two virtuals using the same IP address one listening to port 80 and the other listening to port 443. The port 80 traffic will be sent to the server which will use the HTTP host headers to display the correct site just like now.

The problem comes with the HTTPS site you have two server each hosting the same sites? Is so put them in one pool and add both SSL certs to the Virtual using the link below

http://support.f5.com/kb/en-us/solutions/public/13000/400/sol13452.html?sr=32430737

The problem you will run into is if the client does not support TLS hostname then the LTM will not know which cert to pass back to the client and will pass back the default cert which in your case has a 50% chance of being the correct cert. Now if most of your clients support this you should not have a problem.