I've got a couple questions for you...

What kind of flying do you like? What manuevers do you find yourself trying to do with your trainer? The Tiger 60 could be the opposite of what you need. On the other hand, it could be perfect. Either way, modification to the design and control system is really NOT needed.

Why do you want seperate elevator halves anyway? Pull pull is fine, but you will need to route some tubes through the fuselage and find a decent location for the servo. It's not an easy thing to do on the elevator on an airplane that is no designed for it to begin with. I can't tell you how to do the pull-pull on the two elevators, but can tell you it's not worth the trouble. I vote against it...

If you want more precision with the controls, pull-pull on the rudder is very important. That would be much easier to setup, but again it's not really worth it on this airplane IMHO.

If you want to enlarge the control surfaces so it is more maneuverable and will do everything quicker and tighter, there might be a better choice of airplane for you.

A Stick can be throw around more than a Tiger 60...They are great airplanes. The Ultra Stick is a really fun airplane...

This all really depends on your flying style. I wouldn't recommend changing the design too much. It's a really great airplane to begin with. It's a proven design and there is a reason it's so popular. If fairly fast flying airplane, but not a real great aerobat. It will loop, roll, spin, and knife edge, but that is about where it ends. Do you want more?