Hi Brian, and welcome. While I don't have to worry much about theft, I do get very tired of carrying rolling stock in and out of my house. Last year I attended the National Garden Train Show in Nashville and got to tour many outdoor layouts, and discovered I was not alone in the "carry rolling stock" issue. One common solution I observed was the running of a track spur into sheds for parking whole trains. As most of the layouts were either on battery power, or in the process of converting to battery power (as I am), they used simple wood shelves with either grooves cut in them or strips of trim to park everythjing...no sense using up lots of expensive brass track just to store rolling stock. I am in the process of setting up such a storage system, but it occurs to me that it might serve to alleviate your theft concerns as well, if you can run track to a nearby back yard shed. Here are some photos. Hope this helps.
BTW, at 76, a raised track layout is vital. I too did not want to run tons of dirt and rock, so I used 4 x 4's to lift the roadbed about 30".