No issues with CAD on the OP's Jeep. Chrysler dropped that system about 10 years before the OP's XJ was built.
Getting rid of the D35 also means getting rid of ABS. Do your homework on that project. It is a common thing to do.
Going to 15" wheels means you are giving up a WJ brake swap down the line. I would be slow to make this change until after you finish getting your rig to the weight you are likely to be traveling at. You may find you want those larger brakes. OTOH, you may be fine with Black Magic pads. There is more than one way to skin this particular cat. Just know what options you are excluding when you make your choice.
For the tire size you want to run you should be fine with the D30. If anything, when it comes time to re-gear, consider stepping up to 30 spline axles. That is probably your best bang for the buck up front.
For the rear, look for a '97+ Chrysler 8.25. That will get you the larger 29 spine axle shafts. '95 and down ran 27 spline shafts. '96 you have to check when it was made. I think April of '96 was the change.
Another, but harder to find, option for the rear would be a factory XJ D44. These are tough to come by. They were probably only available for one year (1987 I think) and everyone wants one.
Yet another option is a Ford 8.8 out of an Explorer. These are a popular option, but they require welding on spring perches. The nice thing about the Ford 8.8 is that if you hunt around you can find them with 4.10 gears, limited slip carriers and disc brakes. When you compare the cost to re-gear one axle and install a custom brake system to the cost to weld on some perches you may find the Ford 8.8 is the most cost effective option. OTOH, if you want to install a selectable locker then you might as well go with an axle housing that is already set up to bolt right in because either option is going to have the cost to set up gears.