front end/back end

Yes, you can set up the routing like you are talking about. I think you need to set up a routing group in Exchange to do this.
Unfortunately, I don't know how to do this. I haven't touched Exchange in a couple years, and I don't remember the setups. But someone else here should be able to step in and give you some pointers.
But I do know that you can have one Exchange server route mail to another server for transmittal, as a type of gateway server.

Why would you want to do this? Front end servers are designed as "single point of contact" gateways for the Exchange Organisation, and you shouldn't really have mail stores or any other stuff running on them.
Personally I would invest in creating arelay server at the backend that you make the SMTP bridge head for the organisation, so you main Exchange Server passes all mail to the relay - change your MS record in the outside world to relay all mail for your organisation to that server and then use contacts to make the choice as to where all of the mail goes, I have done this where I work and it works fine - if you need further information I can e-mail you a sample schematic for the system.