Correct me if I'm wrong but I believe that when the T-case is in a 65-35 mode then the t-case works like an open diff. It only takes one wheel to loose traction in order to lose power to all other wheels. That's not ideal.

Last time I checked the seals were still available (few months ago).

I think that a rebuild with new seals is the best way to go. Especially since you need hydraulics to engage the rear axle lock (Which by itself could be better than 4 wheel drive)

I was thinking about a different solution of bypassing the transfer case hydraulics:

Solution #1:
Internally modify the T-case to be in 50-50 mode and then have a custom front 2-piece driveshaft with a mechanical sleeve that would engage/disengage the front axle.

Solution #2:
Internally modify the T-case to be in 50-50 mode and then have a custom manual locking hub on one of the front wheels. The problem is that you would have to get out of the car to engage it

Solution #3:
Internally modify the T-case to be in 50-50 mode and just have even tires and wait till something goes wrong