You can do it but there are problems and you can damage something without end limits. You need something to "decode" the position switches to tell you when you're in 4HI. 4LO and 2WD are easy -- they're at the end of the motors rotation on each end.
I'm designing something like you're talking about but with some features to make it a little easier on the motor drive if you push the thing to the end of travel and stall the motor.
But in the meantime, you can use something like the switches used for sunroofs and power windows. They usually have two black ground wires (which you'll connect together and ground), a blue or other colored power wire, and a pair of wires to go to the motor.
What you do is connect appropriately fused (15 amps generally) 12 volt power to the power wire going to the switch, ground the black wires, and run the other pair to your motor wires which are usually thick orange and yellow wires I believe.
Now when you use the window switch, you'll be instead driving the t-case motor in different directions. But it goes from one end to the other pretty quick and you need to "bump" it into 4HI. But where exactly is 4HI? Without decoding the switches it's hard to tell.
That's what the circuit I'm making does. It's pretty simple but it does have relays, led's and resistors and so forth in it. But no computer, no transistors or other logic and it does shut the motor off automatically at each end of rotation and it shows you where 4HI is so you can bump it into place.
I'll be posting separately on it sometime by this weekend after I finish testing it and making the final version in my basement.